John P. (Jack) Studnicky has just turned 40. He's 6-foot-2, weighs 195 and has an income in the six-figure bracket.He lives in two redone. put-together apartments on the 17th floor of the Alexandria House condominium. That's where he also earns part of his livelihood at the moment.

His firm, JPS Associates. has a contract to market the Alexandria House apartments, of which Alexandria House, Inc., a subsidiary of Chase Manhattan Bank, is the owner. The bank foreclosed late last year on Magazine Brothers, who built and nearly finished the 23-story building on the northern fringe of Old Town Alexandria. But sales were slow in a depressed market. That was three years ago.

Studnicky, who is not a real estate broker, says that his specialty is motivation, stimulation and innovation. Since he took on the Alexandria project about five months ago and got a campaign going three months ago, he and his sales staff (Peter Charles, Frank Pulli and hostess-assistant Rebecca Lewis) have brought in 150 sales contracts. Before Studnicky took over, 31 dwellings had been sold over two years. Now about 27 units, depending on how it went this week, remain unsold. And prices have been raised in recent weeks, since the promotion and sales effort took off, he said.

Earlier Studnicky had quickly sold out the 9400 condominium at Ocean City, where Anderson-Stokes was the original developer before Chase Manhattan Real Estate Investment Trust took over the deed in lieu of foreclosure. Lowered prices and 8 per cent financing helped turn the sales tide, Studnicky said.

But this former Marine and native of Newark, N.J., refuses to give all the credit for selling turn-arounds to lower prices and better terms. He contends that you have to "get things bubbling and buzzing . . . establish some excitement."

First, this consultant, lecturer and teacher stimulates his own sales staff "so the prospect meets a turned-on salesperson." Then Studnicky orchestrates a marketing program.

At Alexandria House, it included getting a $600,000 commitment from Chase Manhattan to finish undone construction, put up an Alexandria House sign, some flags and arrange party-like visits for prospective buyers. And - not least importantly - he got the earlier owners already living in AH turned on to become informal selling agents to offer special incentives (like a referral certificate of a $1,000 discount to friends who might want to buy.)

But the Studnicky touch, which has also been applied to Suburban Oaks Apartments in Pikesville, Md., and to Imperial House in Baltimore. doesn't call for a total formula approach.

"Each project must be analyzed for what it is - its strong and weak points. Then you take it from there. But the key is absolute concentration, seven days a week at a stretch and up to 20 hours a day. I overwork myself and my salespersons. But we get our breaks and rewards too," he said.

After the Marines, Studnicky was a construction laborer in Philadelphia so me years ago. Then he got into swimming pool selling and made $100,000 in a year. Then he read a book ("Think and Grow Rich," by Napoleon Hill) and that convinced him of the value of "singleness of purpose."

As a born-again salesman, he then be gan to train others to sell, to lecture (at $1,000 a crack sometimes) and to teach principles of management and other things. He also planned to launch a "retreat for executives and middle management persons facing the crisis of losing or changing jobs."

That's when he got involved a few years ago at Ocean City, where a close friend introduced him to Chase Manhattan people.

"He's a marketing genius," said Peter Mullins, an assistant treasurer working in real estate for Chase. "He knows how to create a new atmosphere. He's exciting himself and passes it along to everyone else. So, if he does a job, his fee is worth it. He still has a way to go at Alexandria House - to get all of the units sold and to settlement."

Not only does Studnicky live in his own redesigned apartment on the 17th floor of Alexandria House, he also has plans to buy the other eight apartments on the floor and rent them. Salesman-broker Peter Charles also has bought a unit and so have some other professionals in real estate.

Apartments range now from the $40,000 level for one bedroom to $90.000 to three bedrooms, with the price per square foot of space over $50. Some prices had been reduced as much as $20,000. "They were unrealistic," says Studnicky. But as sales move ahead, prices are moved up. Mortgage terms were reduced to 8 3/4 per cent. Downpayments are pegged at 10 per cent for owner-occupants and 25 per cent for "investors" who do not plan to live there.