The Manufactured Housing Institute, the Arlington-based trade association representing mobile and modular home manufacturers and their suppliers, will exhibit three mobile homes Oct. 16 and 17 between the Air & Space Museum and the Botanical Gardens on the Mall. The institute also reported that 139,866 mobile homes were shipped to dealers in the first six months of 1979, an increase of 1 percent over the total for that period in 1978.

The Metropolitan Washington Council of Governments has scheduled its third housing rehabilitation specialist training course, beginning Oct. 25, in conjunction with the Department of Agriculture. The course is designed to aid individuals working in the public and private sectors of residential rehabilitation. Cost of the 74-hour course is $300. For information, call 223-6800, ext. 490.

Ryland Homes has opened sales of traditionally styled new houses at Parkwood II in Glen Burnie, Anne Arundel County, where some low-interest mortgage loans are available to moderate-income buyers through a Maryland State Home Ownership Development program. Detached houses are priced from the $70,000s and semi-detached houses from $51,500. The site is reached from Rte. 3 and Quarterfield Road.

Project Funding Corp. of Washington, headed by Sondra Linden, has arranged financing for Chestnut Hill Gardens apartments in Newton, Mass. The two towers of 428 units were insured under the FHA section 221(d)(4) rental program for a mortgage of $21 million.

The Northern Virginia Builders Association's manpower training program recently graduated 23 pre-apprenticeship students. They took courses in air conditioning, heating and carpentry.