A total of 105 of the 450 new home projects being marketed in the Washington area have units with base prices of $100,000 or less, according to a new survey by the Quixsearch brokerage service at Woodward & Lothrop.

Of the 105 projects, each with at least five units for sale, 61 are in Maryland, 43 in Virginia and one in the District, Quixsearch said. Most of the units under $100,000 are town houses; 22 of the 105 projects sell detached homes.

The study, done by Quixsearch's Belinda Jacobson, showed that most of the housing in the under-$100,000 category is being built in the Washington area's outer perimeter.

Fifteen of the developments are located along the I-270 corridor from Gaithersburg to Damascus in Montgomery County, 13 are in Largo and Bowie in Prince George's County, 17 are in the Woodbridge, Occoquan and Manassas areas of Prince William County and seven are in western Fairfax County.

IN THE BUSINESS . . . Rouse Co., developer of Columbia, Md., has pledged $500,000 as a matching grant to the 20th anniversary community endowment campaign of the Columbia Foundation, a community group seeking to create a $1 million endowment. Since its formation in 1969, the foundation has contributed $750,000 to community and charitable groups in Columbia and Howard County . . . Waverly Park, a 3.6-acre office park, is being developed off the Leesburg Bypass and incorporates Waverly Mansion, an early 19th-century residence . . . The Eugene and Agnes E. Meyer Foundation has awarded a $12,750 grant to MUSCLE Inc., a Washington nonprofit housing development corporation, to help support the salary of a full-time program manager for its vacant housing development program . . . The Virginia Association of Realtors is staging its annual convention in Crystal City in October . . . The second phase of the Potomac Mills Mall opened in Prince William County this week, making it the largest factory outlet mall in the world, according to Western Development Corp., the center's developer . . . Herbert N. Morgan and Guy E. Beatty have sold a 3.2-acre tract at the northeast corner of Fairfax Drive and N. Glebe Road in Arlington for $12.2 million to Rouse & Associates, which plans to build the 347,000-square-foot Ballston Corporate Center on the site . . . Coakley & Williams Inc. has started a "lease with equity" program at Maryland Trade Center III in Greenbelt, a marketing program aimed at securing leasing commitments prior to the start of construction in the fall . . . The Northern Virginia Board of Realtors has given its Realtor Ethics Award to Hilda M. Rochford of Century 21, Sales Associate of 1986 award to Wes Hayfield of Lewis & Silverman Associates and Rookie Sales Associate of the Year award to Anita Nilsen of ERA Wellborn Real Estate Co. Inc. . . . . The most expensive house sold in Fairfax County last year was bought by Defense Secretary Caspar W. Weinberger. He paid $1,235,000 for his home at 1284 Ballantrae Farm Dr. in McLean, according to the real estate reporting service of Rufus S. Lusk & Son Inc. . . . Stout & Teague Cos. have started construction of the $60 million Resources and Conservation Center at 16th and P streets NW, which will be the home for the National Wildlife Federation and Resources for the Future . . . Baier Properties Inc., an investment building firm in Rockville, has bought the $10 million Oakton Corporate Center II from Folger Investments Inc. The center is at the intersection of I-66 and Rte. 123 in Fairfax County . . . Weissberg Corp. and Misner/Daniels Development Corp. have formed Shirlington Gateway Associates, to complete construction and market the 12-story, 200,000-square-foot Shirlington Gateway office building at 2800 Shirlington Rd. in Arlington . . . R. Lawrence Koch Jr., senior vice president at PaineWebber Mortgage Finance in Baltimore, has been elected president of the Maryland Mortgage Bankers Association . . . Mount Vernon Realty recently formed an international property consulting subsidiary, Howard, Kent and Associates Ltd., which primarily will act as a conduit for direct investments and income-producing property, chiefly in Europe . . . Construction has started on 500 E St. in Northwest Washington, a 251,000-square-foot office building being developed by Boston Properties and First City Properties.

PERSONNEL FILE . . . Robert R. Strott has joined KMS Group Inc., a developer based in Columbia, as vice president. The firm has started construction on an 84,000-square-foot, five-story office building at 5801 Allentown Rd. near Andrews Air Force Base . . . Edw. R. Carr & Associates has promoted J. Michael Belle to vice president of its home-building division . . . National Corporation for Housing Partnerships has promoted Roger L. Salen to vice president of its Real Estate Securities Inc. subsidiary. Sam Stern has been appointed vice president for development of Capital Commercial Inc., another NCHP subsidiary . . . H. James Kostyk has joined Interstate General Corp., a developer based in San Juan, Puerto Rico, as vice president for property management to oversee the firm's Washington-area holdings . . . Kettler & Scott, a Tysons Corner developer, has named two new vice presidents: Alvin B. Veirs Jr. for operations and Anthony R. Lowstuter Jr. for construction . . . William W. Merriam and Allan Lipsky have been named vice presidents at the J. E. Robert Co., an Alexandria firm that specializes in management and disposition of financially troubled real estate projects . . . Savage/Fogarty Cos. Inc., an Alexandria developer, has named James A. Fetgatter as executive vice president. . . Coldwell Banker Residential Real Estate has promoted Jim Peterson to executive vice president/general sales manager for the firm's Washington group. . . John C. O'Neill has been named president of Mulligan/Griffin Property Managers Inc., a Rockville firm.