Shao Ti Hsu, the Washington landlord who for years housed thousands of lower-income families in some of the most rundown apartment buildings in the city while he resided in a $300,000 home in Potomac, says he likes his newest home--in the D.C. jail.

"I'm happy here," said Hsu, 66, during an interview at the jail, where he is in protective custody, separated from the other inmates. He is serving a sentence of 20 months to seven years on a perjury conviction stemming from a 1975 civil court hearing about one of his Southeast Washington properties.

"The food is fairly good," Hsu said. "It's not a big steak every night, but it's fairly good. You get free hair cut, free meal service, everything free, including room and board, all free," he says with a giggle, fingering his light blue prison overalls, which he wears with black wing-tipped shoes.

Hsu, an engineering professor at the University of Maryland, has been charged in 49 criminal cases involving hundreds of housing code violations in the District during the past 10 years. But this is his first prison sentence.

At his sentencing two weeks ago, the slender, bespectacled professor pleaded with D.C. Superior Court Judge Peter Wolf not to send him to prison, saying that he "might die" there because of his high blood pressure.

But Hsu's pleas failed to move the judge, who called him "a white collar criminal . . . for whom the ends justify the means, certainly when it comes to money."

Now, after receiving vitamins and pills for his blood pressure, Hsu says he is making the best of prison life.

"I have a philosophy," he explains. "I am happy in jail or out of jail. No matter what they do to me, I'm happy. You have to learn to live that way."

He has, he says, "no regrets" about the past. Instead, he describes himself as a hardworking man who merely tried to succeed in the capitalist society he had embraced as an immigrant from China.

"In this country, it's a capitalist system. People here have the habit of talking about money all the time," said Hsu, a soft-spoken man who seems to always be smiling.

In 1976, Hsu was named the city's most frequent violators of city housing code regulations. The label was unfair, he maintains. "All over the area, other buildings had the same problems as mine . It was not because I didn't manage my buildings right. This was a problem across the whole city," he said.

While Hsu calls his former tenants "good people" whom he felt sorry for, he also blames them in large part for the condition of his buildings. "To fix everything to top-notch condition, that was very difficult. The tenants, they damage things."

Hsu, who once managed about 1,000 apartments in the area, says he now occupies his days going through the calling cards he has accumulated from several dozen lawyers through his many court cases, and is trying to decide who should represent him on his appeal of the perjury conviction.

He is also working out the details, he says, of two research projects, one on solar energy-powered air conditioning and another on an alcohol-fueled automobile engine.

Hsu, who has written an engineering textbook, said he hopes to resume teaching at Maryland. But last week, university chancellor John Toll said he has asked the school's board of regents to fire Hsu on the grounds of "willful neglect of duty."

When he is finished with work and personal matters in his cell block, Hsu says, he sings opera songs he learned from his wife, a musician, or patriotic songs he remembers from his native China.

Often, he says, he helps arrange bonds for other inmates. "I know all the bondsmen in D.C. and Maryland," Hsu says proudly. "I get nothing out of it. I'm a good-hearted person. Especially poor people, if I can help them, I will," he adds.

At his peak, in the mid-1970s, Hsu owned 512 rental units in low-income areas in the District and Prince George's County. In 1974, he filed a financial statement with the court that said he had a net worth of $2.1 million, including seven cars (one Mercedes, four Buicks and two BMWs), his house in Potomac and a house and a cooperative apartment in Cambridge, Mass.

But it was also during this time that District officials began charging Hsu with housing violations that included failing to provide heat, hot water and gas to his tenants, whom he housed in trash, roach-and-rodent-infested buildings that often did not have adequate lighting or fire extinguisher systems.

D.C. Superior Court Judge Tim Murphy, who presided over a 1976 case against Hsu, said he once considered sentencing the landlord to live in one of his own buildings, but that such a sentence would constitute "cruel and unusual punishment."

Hsu was forced to pay at least $5,000 in fines for District housing code violations, according to Assistant U.S. Attorney David S. Krakoff, who prosecuted him on the perjury charge. But Hsu never served a prison sentence.

Besides his cases in the District, Hsu also had several cases filed against him in Prince George's County, including convictions for housing code violations and for assaulting a tenant organizer at one of his buildings on one occasion, and assaulting an 11-year-old boy who tried to place garbage in a can on one of his properties on another occasion. For those convictions, he was fined and was placed on probation.

Hsu says making money "was never as important as engineering" to him, but once he dabbled in Washington real estate and found that "in this business, you can make money very easy if you do it right--a large amount, not peanuts," real estate soon became as much a passion as engineering.

Hsu said he realized this in 1969 when he and another mechanical engineering professor organized a company to service air-conditioning systems and boilers in 25 apartment buildings. Hsu and his partner hired students to do the work and charged landlords $6,000 per year for the maintenance at each building. "That's $150,000 a year we were making," Hsu says. "That's a lot more than a university professor's salary."

Soon, Hsu said, "I begin to think we can make more money if we own these buildings. So I started to own buildings and then more and more owners would say, 'I'm really sick of this building, would you take it over, Dr. Hsu?' So I become a big landlord and that's where the trouble started for me."

At his sentencing, Hsu's attorney, Jeffrey Lee Greenspan, said that Hsu no longer owns properties in the District, no longer has a license to rent properties in Maryland, has been evicted from his house because he failed to pay creditors close to $900,000 that he owed in court judgments and is virtually bankrupt.

But Hsu says he still owns properties, though none are now in his name. He would not specify how many properties he owns or his current net worth.

He says he will, however, stay out of real estate management "because there's too much headaches."

Hsu was charged with perjury in 1976 after he stated at one of his trials that he never received a court order to make certain repairs at one of his Southeast Washington properties. It was later established in court that he had received the order. The jury deliberated 15 minutes before finding him guilty.

As in most of his trials, Hsu had served as his own attorney. When he appealed his conviction, the D.C. Court of Appeals ordered a new trial on the ground that Hsu may not have adequately understood the severity of the charges against him.

He was again found guilty of the perjury charge in March.

As for the future, Hsu says, he hopes to get his latest perjury conviction overturned. Afterward, "I will get my family back together and enjoy our life together, and I will keep on working until I die."