The French chateau house of departed football coach George Allen and his wife, Etty, is being offered for sale by several Northern Virginia brokers. One of them, Madeline Zung, said the asking price is $675,000.

Veteran real estate broker William C. Stuart III insists that mortgage money is available here - although at an expensive 10 percent interest rate - for mortgages on resale houses. Stuart thinks there is a public misapprehension that loans on resale houses are almost unavailable, and maintains that this is a factor that has slowed the resale market in recent weeks. Two of the larger savings and loan associations in the District, National Permanent and Columbia Federal, are making loans but requiring down payments of 25 percent. The largest S&I, Perpetual Federal, is making mortgage loans onlu to its depositors.

You've heard so many times, "I couldn't afford to buy my own house at today's prices." Well, Mark P. Riedy, executive of the Mortgage Bankers Association, known an economist who did just that in the East Bay section of San Francisco. The fellow and his wife bought a house for $53,000 in 1972. They sold it for $95,000 in 1976 when their marriage was foundering. But they reconciled and decided to buy back the house - and paid $135,000.

Beekman Place, the complex of 216 town houses that the Lawrence Brandt firm is building at 16th Street and Florida Avenue NW, is sold out, a year earlier than the firm expected. Rick Leeds, Brandt's man for property management and sales, said that the last of the houses will be finished later this year. The last of the contracts ranged from $34,000 to $106,000 up at least 20 per cent from the prices Brandt set when Beekman Place was opened in September 1976.