There are indications that buyers here and nationally are beginning to return to the resale market.

Decreasing interest rates and the availability of more mortgage investment dollars are the reasons for the slight improvement in the residential market.

The level of sales is still low, especially for new houses, but many real estate brokers here are anticipating that business will pick up through summer and fall.

New optimism is evident among brokers who had trouble surviving the downturn in resales that began last fall. And at least one firm, Century 21 of Springfield, stoutly maintains that it has escaped the general market malaise.

"We had the best first quarter in our four-year history," said Joe Chopek, principal broker and president of the firm, which has two offices in Northern Virginia.

Chopek said that the $9.3 million in houses sold during the first quarter was 96 percent higher than a year earlier. The firm sold $26 million in houses last year. Sales continued to pick up in May, he said.

"There are a lot of reasons (why business has been so good) involving training, personnel and motivation," Chopek said. "But one of the principal factors is our method of operation. We are a public corporation, with Metro Capital Corp. holding a 10 percent interest.

"More importantly, we were founded with myself, Kenneth and Patricia Smith and Kenneth and Louise Aiken as stockholders. Then we offered an opportunity for sales persons to become stockholders too."

So far, three of them -- Daniel Canada, Marilyn Jett and Gary Mazur -- have done so.

Canada said that the incentive of being able to become a part-owner is important.

"I did well in sales after joining the firm last year and I had some money from a piece of property that I sold," he said. "So I put $8,000 into stock in this firm. It's a motivating factor to be able to get a piece of the pile right away."

Chopek, 33, said that the stock incentive plan is open to any of the firm's agents who make more than $20,000 a year in commissions and is accepted by the board of directors.

"It's really a matter of increasing incentives to do well," he added.

The 40-member staff in two offices now includes eight shareholders. "Individual agents who are shareholders pass on their enthusiasm and drive to the new people," Chopek said. "Every six months, we make the offering. Having this option is also a plus in attracting new sales persons.

"The stock plan also enables a firm to keep sales persons who might otherwise want to become brokers and open their own firms. That's a natural goal in this business."

Louise Aiken, assistant vice president and case processing officer, is not an agent, but her husband is an associate broker. "People are still looking to residential real estate sales for a career," she said. "Like those of us in this office, they also have confidence that the market will improve."

Realty firms with stockholding options for sales persons are not common in this area. One principal broker, who laughed when asked why this was so and then requested that he not be named, said: "It's spelled E-G-O."

Robert V. McGrath, president of the Northern Virginia Board of Realtors and an executive with Peck Properties, said that his former Carriage House realty firm had been founded with stockholders and had 10 at one time.

"I'd say that it worked well for us and seems to be all right for a few others. But generally, the principal broker likes to hold control if possible," he said.

Lykes Boykin, the Northern Virginian who heads the multioffice Panorama firm, said that the owner-affiliate program of Panorama offers an opportunity for the head of a realty brokerage office to retain profits while operating as part of Panorama in terms of policy and procedure.

"The stock-owning principle among firms is part of America's free enterprise system. I'd like to see every American own his own home and his own business," he added.

Incentive and motivation play a major role in the operation of any business.So does the retention of top sales persons. Most firms pay higher commissions to top producers. Some firms have so-called 100 percent commission programs for outstanding sales persons. That's the basis of the RE/MAX national franchise concept, which is handled here by Frank Altobelli of College Park.

As RE/MAX franchise owner for the mid-Atlantic region, Altobelli has sold 22 franchises. He said 11 offices are open and doing business. "We see about 35 of our franchises in this region by the end of 1981," he said. "Selling is a full-time career for top professionals and some are willing to pay a share of running an office to get a full commission."

Altobelli said that the shared monthly expense might cost an individual sales agent as much as 20 percent of his 100 percent commissions or as little as 8 percent. "There are three basic categories of monthly expenses: management fee, shared branch office expenses and personal expenses," he said.

Real estate professionals are expecting a continued upturn in sales activity if mortgage rates continue to soften. Conventional mortgage loans are generally available for about 14 percent and moving downward. The FHA-VA rate ceiling was lowered earlier this week to 11 1/2 percent, reflecting market conditions.

S & Ls are now reported ready to remake existing loans if the purchaser is willing to pay a higher rate -- on a negotiable basis -- than did the seller.

Until effective mortgage rates fall at least to the level of 12 percent, buying and selling of residential properties are likely to be below average. Additionally, there is a need for renewed public confidence in terms of the general economy.