Tenants associations at the huge Van Ness Centre just off upper Connecticut Avenue NW have signed contracts to buy their two buildinds for about $600 million. If the sale is consummated, it apparently will be the most expensive purchase ever by tenants in the city.

The tenants will buy the buildings themselves for more than $51 million from Van Ness Properties. The Chevy Chase Land Co. owns the land at the complex. Tenants are expected to meet next week with Chevy Chase officials to negotiate the sale of the land at a cost of about $8.7 million.

Tenants signed their contracts with building owners Thursday. "We've got the building. We're very pleased," said Louise Sissman, co-president of the tenants' group.

Tenants in the two buildings, which have a total of 1,058 apartments, have not decided whether to convert to condominiums or to cooperatives. Both groups raised well over the amount of deposit money required to buy the building, tenant association officials said.

In the east building, tenants expect to buy units at prices ranging from $30,000 for small efficiencies to about $104,000 for a three-bedroom unit. In the south building, prices for tenants are expected to range from slightly under $45,000 to more than $111,000 for some two-bedroom units with two baths, according to Franz Wolf, vice president.

Units sold to the public probably will be priced considerably higher. At this point, tenant officials said, about half the tenants in each building are expected to buy units.

Van Ness was the focus of controversy earlier this year when a firm controlled by developer Conrad Cafritz sent tenants letters notifying them that the firm was buying the buildings and planned to convert them into cooperatives.

Cafritz's firm, Investment Group Development Corp., already had changed one of the three buildings in the complex to cooperatives. But for a year now, the city has had a moratorium on most condominium and cooperative conversions unless tenants agree.

City housing officials called the notices from the Cafritz firm a "blatant challenge to the moratorium. The city's Rental Accommodations Office issued a restraining order invalidating the notices in late February.