A nonprofit real estate industry coalition has embarked on an experimental program to convert a group of vacant city-owned slum apartments into low-cost condominiums as an alternative to higher priced single-family dwellings.

The city's urban renewal department yesterday gave preliminary approval to a proposal submitted by the D.C. Housing Industries group to convert four buildings containing 114 units into condominiums. The group is a nonprofit organization composed of representatives from the city's five major real estate-related trade associations.

James G. Banks vice president of the group and several city officials said they believe that with the high price of housing in the city, condominiums are the only route to home ownership for low and moderate-income families.

"Obviously with the proce of single-family homes at $45,000 and up, most of these families would never have a chance of owning a home if they could not buy an apartment," Banks said. "Condominiums are one of the few avenues open for-low-and moderate-income families for home ownership."

The proposal marks the first time that condominiums, usually thought of as dwellings for more affluent owners, would be priced specifically for sale to families earning between $10,000 and $14,000 annually. The proposal calls for the units to sell for prices ranging from $12,000 to $20,000.

The four buildings sought by Banks' group are at 1st Street and New York Avenue NW., in the Northwest One urban renewal area. Under the group's plan, the 114 units will be converted into 88 condominiums.

D.C. City Councilwoman Nadine Winter, who heads the Council's housing committee, said that while she supports condominiums for low and moderate-income owners, she was skeptical of the group's success.

Several times the city has ear-marked housing for poorer families, she said, only to find in the end that the sales prices were beyond their reach.

"It looks bad to say they (the housing) will be brought in for these families and we don't do it," she said.

To keep the prices of the proposed New York Avenue condominiuns low, Banks said the group asked the city to give them the buildings free of charge.

Carroll Swanson, director of the neighborhooh improvement administration under the city's housing department, indicated that the city is looking either to give away the buildings or in some other way ti subsidize the project. "We want to do this project," he said.

The Housing Industries Group is composed of representatives of the city's savings and loan institutions, banks, builders, realtors and real estate brokers associations. It recently completed the renovation of 35 sinlge-family houses in Shaw that were sold to moderate-income families.

The city has owned the now boarded up, vacant buildings on New York Avenue since the late 1960s when they were purchased as part of the Northwest One urban renewel area.

Since 1973, the city government has tried twice unsuccessfully to sign an agreement with private developers to rehabilitate the buildings. The first developer could not obtain financing, and the second backed out because it disliked the various guideliness imposed by the city.