Horizon Condominium Corp. has begun selling condominium apartments in the 291-unit Horizon House at 1300 Army-Navy Dr., Arlington. The 11-story building formerly was a rental property. Prices range from the mid-$30,000s to the high $80,000s.

The Holladay Corp. is being honored for its remodeling in Bethesda of the Bradley Boulevard apartments, a town house condominium project now called Kenwood Forest. The firm will receive the Oliver Owen Kuhn cup for "attractive commercial properties" Tuesday from the Bethesda-Chevy Chase Chamber of Commerce. The Bagley-Soule-Lee firm, architect for the rehabilitation, will also receive an award.

The Falls Church office of Cameron-Brown Co. recently arranged $6.2 million in permanent financing for the United Plaza office building in Springfield. The nine-story twin-towers will be completed next year. The builder is United Joint Venture. Kasen-Svalbe is the architect.

Town & Country Properties Inc. has opened an office in Camp Springs. It is the firm's first branch in Prince George's County.

DEAR Realty Inc., which is based in the District, has opened a branch office at the Dodge Plaza Shopping Center on Landover Road in Prince George's. Charles G. Sanders is the broker and Ruby Bullock is the manager.

The relations of condominium associations with city governments will be the topic June 12, when the area chapter of the Community Associations Institute meets at the Key Bridge Marriott. CAPTION: Picture, CALVERT PARK - Joggers swing pass the Calvert Park condominiums at 1945-47 Calvert St. NW, a 28-unit project being completed on the former Shapiro tact in Adams-Morgan. Part of the tract has been maintained as a playground. Prices for the condominium units, which are being built by Joseph Gildenhorn and Calvert Park Associates, range from $74,000 to $82,500. By Jack Hayes for The Washington Post