The Washington D.C. Association of Realtors has adopted a new standard contract for sales of cooperatives that will require co-op boards to disclose financial records and pending legal actions to prospective purchasers.

William M. Karas, president of the Edmund J. Flynn Co., which has been active in co-op sales in the city for 65 years, said the Realtors revised the contract in an effort to "make cooperative boards more aware that these things need to be disclosed in today's marketplace."

The D.C. government requires people selling units in condominiums to disclose certain financial information about the condominium association, but the city does not require similar disclosures for co-ops.

But Karas said buyers are becoming more cautious and now ask more about the fiscal health of co-ops before signing sales contracts. While purchasers of co-ops will not be required to use the new standard contract, most Realtors use the standard form as a matter of course.

Under the new contract, a seller of a unit in a co-op would have to provide the purchaser with the articles of incorporation, bylaws and rules of the cooperative, a copy of the co-op's most recent financial statement and a statement of the status of any pending suits or judgments to which the cooperative is a party. The purchaser also would have the right to cancel the contract within three days after receiving the information.

The Baltimore County estate of opera star Rosa Ponselle is for sale because money used to run the home as a museum can be better spent helping young artists, officials of a foundation said.

The asking price for the Villa Pace estate, including a sprawling Mediterranean villa on 40 acres, is $2.75 million. The estate was Ponselle's home for 40 years and has been a museum since her death in 1981.

Elayne Duke, president of the Ponselle Foundation, said this week that Villa Pace is being sold because it is draining funds from the organization's endowment.

"It costs $150,000 annually to run the museum, and, because of those costs, the foundation decided it was time to take a new direction," Duke said.

"We will be sponsoring opera-center programs for worthy young artists in the San Francisco, Houston, Chicago and Metropolitan Opera companies, plus expanding the annual Ponselle International Opera Competition," she said.

"It was our feeling that we can best perpetuate Rosa's legend by supporting those efforts. But we can't do this if we use up all our money maintaining Villa Pace," Duke said.

Judy Baer, director of a group that has long battled development in the area, said her organization is "concerned" that Villa Pace is up for sale and wants nondevelopment provisions included in any sales agreement.

Duke said any sales contract would require that the character of the estate be retained and that it not be subdivided.

Ponselle's costumes and other belongings will be donated to Yale University, the Smithsonian Institution and the archives of the Metropolitan Opera and Covent Garden in London, Duke said.

"We don't want to slight Baltimore, since Miss Ponselle lived here for so much of her life. Certainly, we'll give some things to Baltimore, if they can be accommodated here," she added.

An empty, 115-unit condominium complex that once was billed as Pittsburgh's "most prestigious address" was sold at sheriff's sale this week for $20,763 to a bank owed $30 million by the building's developers.

Mellon Bank announced it has retained Maywood Co. to market the 25-story Trimont, where the developers had failed to sell a single unit a year after erecting the angular tower atop a bluff overlooking the city's three river valleys, downtown skyscrapers and rolling suburbs.

Trimont went on the auction block after the bank foreclosed against Washington Heights Associates, the partnership that built the condos.

It cost $50 million to build, and Mellon's purchase and assumption of debt and penalties essentially gives it the building for nearly $30 million. One loan, now listed at $29.7 million with penalties, has been in default since September.

The complex has space for 30 retail shops, two restaurants, a courtyard and a 400-car parking garage. Trimont was scheduled to open last spring, but marketing problems plagued developers, and none of the units -- priced from $179,000 to $650,000 -- was sold. Only 23 interested parties made down payments.

Lincoln Property Co. has sold its interest in Tampa's downtown Harbour Island project and is preparing to sell off other properties around the country because of what it believes is a gloomy future for the real estate market, according to the firm's Tampa representative.

Lincoln and Beneficial Corp. have been joint partners in the major development since 1982. But Mike Hogan announced this week that Lincoln had sold its share to Harbour Island Inc., a subisidary of Beneficial and developer of condominiums on the island.

Lincoln's share of the project was One Harbour Place, a 196,000-square-foot office building; The Market, a 105,000-square-foot retail center; and the 300-room Harbour Island Hotel. The purchase price was not disclosed. Hogan said Lincoln will continue to manage the three buildings.

Hogan said Lincoln decided to sell the buildings because of its gloomy outlook for the real estate market. He said the company, based in Dallas, is predicting a national recession in the next two years and is negotiating the sale of additional property in Tampa and around the country.

"We're trying to build a war chest to ride through rough times," Hogan said.

IN THE BUSINESS . . . Washington Homes Inc. has started construction on an $8 million, 110-unit town house development at the Tanglewood development near Waldorf, and a $14 million, 180-home development at Fredericktowne in Frederick . . . The homebuilding firm of Stanley Martin Cos. reported total sales of $57 million during 1985 . . . Marriott Corp. is opening the Fair Oaks Courtyard Hotel at 11220 Lee Jackson Highway, near the Fair Oaks Shopping Center, next Saturday . . . Kaempfer Co. is planning a 250,000-square-foot office building at 1001 19th St. North in Rosslyn that is designed by I. M. Pei & Partners.

PERSONNEL FILE . . . Brent Clarke has been named vice president in charge of mid-Atlantic real estate acquisitions for Alan I. Kay Cos. . . . Robert Rust has been named president of Miller and Smith Commercial, a subsidiary of the development firm of Miller and Smith Inc. . . . Richard K. Chalmers, architecture dean at Florida A&M, has been appointed vice president for design and construction at Enterprise Development Co. . . . Toni I. Burger has been named president of Harper & Co. Realtors in McLean . . . Bruce Berlage has joined the development firm of William L. Berry & Co. as vice president of operations . . . David Graham has become vice president and chief financial officer of Winchester Homes Inc., which recently sold its 1,500th home. Peter G. Byrnes has been promoted to senior vice president of the firm's diversified business group . . . Harvey Construction Co. of Rockville has named Richard Maggin as executive vice president in charge of construction.