One evening every week, a dozen or so hipsters in their 20’s and early 30’s file into a second-floor office above a deli on Delancey Street. They are aspiring musicians and actors. They work at Trader Joe’s or some do-gooder nonprofit. They are studying fashion design or maybe they just graduated, and like everybody else trying to make it in New York, they want a cheap place to live.

They end up on Delancey Street because that’s where an ad on Craigslist has led them. It is a recently redone office with burgundy-stained wood and bright brass fixtures, and the hipsters hang around and whisper and shuffle through papers. They can’t just hand over their checks to their broker and get their keys the way other people get apartments in New York. These people have to meet their landlord.

Their landlord is Baruch Singer.

To these hipsters, that name might not mean much; but, to any New Yorker who has been around for a while and has a knack for remembering names, that one may sound familiar. It is sometimes preceded in newspapers by the word “notorious,” sometimes by “slumlord,” and sometimes even by “notorious slumlord.”

A few minutes behind schedule on one of those recent evenings, Mr. Singer bounded into the room, said hello to a couple of his brokers, and whispered to his staff. He was tall, thin and wore a rumpled, navy blue pinstripe suit that had the look of having been to the far reaches of the city and back in a single day. His beard was scraggly. Atop his gray hair was a simple black yarmulke. He looked a bit like a philosophy professor as he leaned against the doorframe, clapped his hands together and started his spiel.

“We are very different than any other landlord in New York,” he said. “Our strength is to tell people the truth. I tell you pretty much every reason not to move in, and then, if you still want to move in, we give you a lease.”

He went around the circle, asking what each person did for a living, and then he launched into little bits of colorful history about the buildings they were moving into.

“You are moving into a drug-infested building. You have at least 10 drug dealers in there.”

“The super in your building is brain-dead. The reason I keep him on is because he does excellent work.”

A young man moving to a Clinton Hill building gets a story about a Pratt student who was murdered nearby right around the time Mr. Singer first bought the building 15 years ago. “Unfortunately, we had the murderers in the building.”

He said he buys buildings that the city considers to be “junk.” Most are in Harlem, Hamilton Heights and Washington Heights. He renovates the apartments one at a time as apartments become vacant. Once he gets through the whole building, he redoes the hallways and common spaces. He says he needs tenants to be his eyes and ears against crime and vandalism.

“Everybody we put in are professional people,” he said. “Very nice professional people. We have had people in Cirque de Soleil, Urinetown, Beauty and the Beast. We are a good-luck charm for people.”

One woman who was moving into Manhattan Valley—the pocket just west of the northern end of Central Park—remarked that she was pleasantly surprised that a Starbucks just opened nearby.

“What has happened there is because of what we have done,” Mr. Singer said.

The message, whether he intends it or not: Baruch Singer is not a slumlord. He is a gentrifier.

Mr. Singer traces his troubles to the fall of 1999, when the crusading reporter Jack Newfield wrote a series of articles in the New York Post. The impetus was a bill by State Assembly Speaker Sheldon Silver that would have allowed Mr. Singer to buy a building back out of bankruptcy after the normally allotted time. Mr. Singer said that Newfield, who died in December 2004, merely used him to exact damage on the Assembly Speaker, who attended the synagogue where, at the time, Mr. Singer’s father was the rabbi.

“I sit next to a guy in synagogue who happens to be one of the most powerful people in New York,” Mr. Singer said during the orientation meeting.

The article tied Mr. Singer to a 1995 collapse of a Harlem building at 142 West 140th Street that killed three people and shocked the city. Newfield cited a New York Times story from a few days after the collapse as proof that Mr. Singer managed the building. However, the official building registration, according to the city Department of Housing Preservation and Development, stated that the managing agent at the time of the collapse was not Mr. Singer, but rather one of the owners, Marcus Lehman.

In any case, a year-long investigation by Manhattan District Attorney Robert Morgenthau vindicated the owners of the building and suggested that poor management—whoever was doing it—was not the cause.

“The investigation did not uncover any connection between the general maintenance of the building and the collapse,” Mr. Morgenthau wrote in a letter to the city buildings commissioner. Rather, the D.A. found that mortar in a foundation wall had deteriorated and a collapse was “not reasonably foreseeable within the definitions of the criminal law.”

Newfield’s article acknowledged Mr. Morgenthau’s findings, but it also quoted then–City Councilman Bill Perkins, who held Mr. Singer “partially responsible” for the three deaths and said that he “was the worst slumlord I have ever seen in Harlem.” (Mr. Perkins, now a State Senator, didn’t respond to a request for comment.) And while Newfield used other examples to build a case against Mr. Singer, his alleged connection to the building collapse was the most prominent one, and has, over the years, been repeated so often that it has taken on the aura of the truth, even if it isn’t.

Other news stories have said, for example, that Mr. Singer “controlled” the building, or that he operated it. The Observer twice in the last year, in fact, mistakenly referred to Mr. Singer as the building’s owner. (He ended up buying the property, but not until August 1995, five months after the collapse, according to the city’s online property database.)

The Observer was invited to attend one of the tenant meetings after contacting Mr. Singer for another story, and then was invited back a second time, and also was able to ask Mr. Singer questions about his record. He would not, however, pose for a photo unless he was permitted to see the article before it was printed, which The Observer did not allow him to do.

Mr. Singer, 53, fell into the real-estate business 24 years ago. He was working on a doctoral dissertation in clinical psychology at Harvard while living on the Lower East Side. One day, he got a telephone call from a man named David Disenhouse, a builder in the neighborhood, who was looking for a partner and who received Mr. Singer’s name from Rabbi Joseph Singer, Baruch Singer’s cousin.

On the advice of a friend, Mr. Singer put his dissertation aside and joined forces with Mr. Disenhouse, with whom he ended up working for 10 years before Mr. Disenhouse moved to Israel. Their first project was raising money to renovate a vacant apartment building on the Lower East Side. They quickly moved into Manhattan Valley, and then central Harlem, looking for good prices in areas that were likely to improve.

Mr. Singer proved to have a good eye: In September 2005, he sold a portfolio of 104 buildings that he had collected over 20 years for $450 million, he said, which he reinvested, after paying off loans and investors, into another 40 buildings. He said he now owns about 100 rent-stabilized buildings, of which he has plans to sell about 20.

At times, his reputation has interfered with his investment strategy. In 2000, the U.S. Department of Housing and Urban Development blocked the sale of a building at 437 Manhattan Avenue, for which he was the highest bidder. But, four years later, after Mr. Singer filed suit, H.U.D. sold him the building.

Mr. Singer said that H.U.D., after looking at how he took care of his other buildings, actually apologized and asked him only to promise to make its building “as beautiful” as he had the others. A spokesman for H.U.D., Adam Glantz, said he couldn’t confirm that any formal apology was offered.

“We had heard from the city and we had heard from the tenants that he was not a responsible landlord,” Mr. Glantz said. “In the end, what happened was, we went out to look at a number of his properties, and the survey found that his properties were, in fact, well maintained.”

Since then, the number of city housing violations in that building has decreased from what Mr. Singer recalls was 477 to the 72 that show up now in the Department of Housing Preservation and Development’s online database. Mr. Singer said that the number should drop to eight after the results of a May 15 inspection are entered into the database.

Dealing in “distressed properties” brings its own set of hazards. The question of whether Mr. Singer repairs his buildings fast enough is at the crux of the repeated legal battles between him and the enforcement division of H.P.D. Last December, for example, H.P.D. sued Mr. Singer over violations at a six-story, 43-unit building at 655 West 160th Street, which he had bought in September 2005, according to online city records.

The lawsuit includes 74 pages listing 437 violations on record for the property. Fourteen of the violations had accrued just since the purchase, including broken windows in public areas, illegal bolt locks installed inside apartment doors, and three instances of paint that tested positive for lead. In January, Mr. Singer agreed to settle for $6,000 and promised to resolve the violations in 15 to 90 days, reserving the right to go back to court for an extension if necessary.

He told The Observer he had no choice because, had he gone to trial, he would be liable for more than $1 million for violations that he inherited—and that, because of the cumbersome way that violations are removed from the system, he might have already resolved. “H.P.D. and I settled the case because we knew we’d do the work,” he said.

Officially, H.P.D. maintains that when landlords buy buildings, they buy the buildings’ violations on record, department spokesman Neill Coleman said. But he added that the city’s lawyers use discretion if it appears that a property owner is trying to improve a property in a timely manner. In the case of 655 West 160th Street, H.P.D. gave Mr. Singer about 15 months between his purchase and taking legal action, and tried to work through other means first, Mr. Coleman said.

Mr. Singer and his bank were thinking more on the order of two years: that was the amount of time that his lender, New York Community Bank, had given him to resolve the most hazardous violations, according to the mortgage agreement.

To act faster, Mr. Singer said, is virtually impossible because of the sheer volume of work and of tenants occasionally not allowing landlords access to apartments.

Stung by the media, Mr. Singer enjoys a much warmer and more adulatory reception at his weekly office hours—which he calls the “best reality-television show.” They are attended not just by prospective tenants, but also by business partners who bring him deals, down-on-their-luck acquaintances who seek the informal charity for which he is known, or by novice landlords who come to watch an experienced hand—the best in the business, they say—in action.

As the tenants come into a side room to sign their leases, he sometimes asks them what they thought of the presentation.

“You have a vision,” said one graduate student. “It’s not just about renting.”

Mr. Singer stopped signing and looked up at her. “Pam!” he called out to an assistant. “Pull out the duffel bag!”

Pam came over with a large black duffel bag full of mementoes that former and present tenants had sent him: magazine articles that they had gotten published; an Ebony magazine cover a tenant had posed for; petitions by tenants’ associations thanking him for “finding a solution for all of the vandalism, drug possession and prostitution that was coming out of apartment #5D;” head shots, thank-you notes and so on.

One of those mementoes was a CD by a Canadian folk-rock singer, Angela McKenzie, who lived in the Dunbar, a huge building complex in Hamilton Heights, even before Mr. Singer owned it. (He sold it in the 2005 sale.) When her upstairs neighbor wouldn’t respond to her entreaties to fix the toilet, Ms. McKenzie called Mr. Singer and asked if she could just move to another apartment, which he allowed her to do.

“He took a genuine interest in me and what I do,” she told The Observer. “I think he has an artist deep inside, and he likes to know about what I was doing.”

Mr. Singer ends up renting to a lot of artists, but he doesn’t like to be considered a gentrifier. “We treat you the same if you are paying $1 or if you are paying $1,800 a month,” he said. “We take care of the people who were there before also.”

It is clear that Mr. Singer has an ethical system that values being straightforward and upfront. If a tenant wants to break a lease, Mr. Singer will let him: “You don’t even have to make up an excuse.” If you want to add someone to your lease, you’re supposed to bring that person by to introduce to Mr. Singer: “I like to know who my tenants are.” And never sign a super’s paperwork certifying that work has been done unless it really has been done.

All of which helps to explain why Mr. Singer has come into conflict with hold-over tenants—people who start living with legitimate tenants and who assume the lease when the original tenants leave.

In January, for example, a student named Carolina Sutaj petitioned housing court to rectify housing violations after Mr. Singer tried to get her out of an apartment on Morningside Avenue that she had taken over from her boyfriend. Her lawyer, Stuart Shaw, told The Observer that by having accepted her rent, the landlord had accepted her tenancy. Mr. Singer says that he stopped accepting her rent when he found out; he said that he doesn’t fix apartments where legitimate tenants don’t live.

“We take them to court, and we do whatever the court says we have to do,” he said.

There is an economic benefit for landlords to get those tenants on new leases, of course: They are permitted to charge up to an additional 20 percent in rent even when rent-stabilized units change hands.

H.P.D., meanwhile, says that it is responsible for enforcing the housing code regardless of whether or not the tenants are on the lease, according to Mr. Coleman, the H.P.D. spokesman.

In Mr. Singer’s system, honesty has its rewards. One young woman at a recent lease-signing had moved in with a roommate in one of Mr. Singer’s buildings and then could have tried to take over the apartment outright when the roommate left New York.

“But she was honest,” Mr. Singer said, “and came to us.” And so Mr. Singer remodeled the two-bedroom apartment and gave her a new lease at $1,200 a month—higher than she was paying before, but about $600 less than market rate, he said.

The woman came into the side office choked with emotion. She said she had just graduated from school and, since her father couldn’t afford to give her an apartment, she was grateful that Mr. Singer had.

She said she was reminded of a story in which a man comes into a rabbi’s classroom and none of the students get up to offer the man a seat; then he walks out. One of the students asks, “Who was that?” The rabbi says it was the Prophet Elijah, but that no one had bothered to offer him a seat, and so he left.

“I am reminded of that,” the young woman said. “Do you know what I mean?”

Mr. Singer, who normally takes praise with a humble nod and a thank-you, was too taken aback to do anything more than mumble.