The first development projects at the Lansdowne complex in Loudoun County will be under way soon, according to Xerox Realty Corp. officials, who have announced they will build a $65 million executive conference center and a $50 million corporate campus.

Xerox's 2,267-acre mixed-use project is just one of several planned along the booming Rte. 7 corridor.

VMS Realty Partners of Chicago purchased the land to build the executive conference center and an 18-hole golf course, Xerox said. The 300-room conference center will contain three restaurants, a fitness center and banquet and meeting facilities. It is expected to be completed by the spring of 1990.

Linpro Co. of Philadelphia will build seven to 10 office buildings at its 38-acre corporate campus, which will be part of the 518-acre Corporate Center at Lansdowne. The first building is expected to be completed in March 1989.

The Centennial Cos. plan a 113-acre mixed-use business park in eastern Loudoun County to be called Centennial Dominion Center. The project, a half-mile north of Dulles International Airport and just east of Rte. 28, will have more than 2 million square feet of office and industrial space, a restaurant and a hotel.

Lerner Enterprises of Bethesda is planning a new regional shopping center, Dulles Town Center, at the intersection of Rtes. 7 and 28 in Loudoun County. Lerner said it expects to have four to six major department stores, as well as more than 150 shops in the center, when it opens in the spring of 1992.

New home sales fell 6 percent in December to a seasonally adjusted annual rate of 603,000, the U.S. Census Bureau reported this week.

While most of the country experienced sales at or above the November level, the rate plummeted 51 percent in the Northeast, deepening builders' concern about the outlook for the industry.

"This is a shock to us," said Dale Stuard, president of the National Association of Home Builders, who called on the Federal Reserve Board to reduce interest rates.

Stuard said the home-sale figures have prompted the NAHB to reevaluate earlier statistics that showed a 16 percent decline in housing starts last month. The NAHB had said the average of November and December housing starts was generally consistent with analysts' expectations.

"We're not forecasting a recession," said NAHB chief economist David Seiders. "Obviously, it could happen. The risks are high."

IN THE BUSINESS ... The median home price in the nation's leading metropolitan housing markets rose 6 percent in 1987, from $93,680 to $99,260, according to a study by Chicago Title Insurance Co. The median price means half the homes sold for more and half for less. The average home price, however, rose 16 percent to $133,410, because of a disproportionate number of very expensive home sales ... Construction contracts in the Washington metropolitan area rose 6 percent in 1987 above 1986 levels, to $6.823 billion from $6.41 billion, according to a survey done by the F.W. Dodge Division of McGraw-Hill Information Systems Co. Nonresidential construction increased 6 percent, to $3.088 billion from $2.924 billion; residential construction rose 7 percent, to $3.735 billion from $3.485 billion ... The Virginia Association of Realtors reported that statewide home sales in 1987 were down 8.7 percent compared with 1986 home sales, but that it was still the second best year for sales in Virginia. Sales in 1986 were the best ever in the state ... The National Association of Realtors reported that the national housing affordability index declined 0.5 percent in December to 116.6. The December index means that a family earning the median income of $31,100 had more than 116 percent of the income needed to qualify for a conventional loan covering 80 percent of the national median existing-home price of $84,400 for that month ... The Suburban Maryland Building Industry Association will offer a free, eight-week, full-time construction craft training program beginning Feb. 15. A class of 20 will learn carpentry, plumbing and electrical wiring. Applicants must be residents of Prince George's County between the ages of 18 and 26. For more information, call SMBIA at 572-5900.

PERSONNEL FILE ... James A. Donohoe III has been named president of the Donohoe Cos. ... The Federal Home Loan Mortgage Corp. (Freddie Mac) has named Douglas E. Whiteley senior vice president of risk management ... Signet Bank/Maryland has promoted Douglas Durans to senior vice president in the bank's real estate finance division ... Gary W. Michael has been named president of Kenneth H. Michael Cos. Inc., a Riverdale commercial real estate services firm ... Carol M. Perrow has been named vice president of the Kenneth H. Michael Property Management Co. ... Thomas M. Stevens, Virginia regional manager and vice president for Shannon and Luchs Realtors, has been installed as the 1988 president-elect of the Virginia Association of Realtors ... Charles B. Carter has joined Centennial Investment Corp. as a vice president ... Kenneth A. Fulmer has been named executive director of the National Association of Industrial and Office Parks.