The first Urban Ventures School, a one-week course for people interested in the business of housing rehabilitation, will begin here Oct. 21. Sponsored by the National Savings and Loan League and the Department of Housing and Urban Development, it is designed to encourage more entrepreneurs to enter the housing rehabilitation field. Information is available from the director, Ray Niblack, at 331-0270.

Four Washington area appraisal organizations will hold a roundtable discussion on current real estate problems at the Ramada Inn in Beltsville Oct. 22. Information is available from Melville Peters, 937-7000.

Workshops on saving energy by reducing home heating costs will be held today, Sunday, and Oct. 20 at theAnacostia Energy Alliance office at 2027 Martin Luther King Ave. SE. Information is vailable from Vincent Kosker, 889-7932.

The Veterans Administration has increased the maximum interest rate for guaranteed loans on mobile home purchases. The rate was raised from 12 to 12 1/2 percent.The last previous rise in the ceiling was made in 1973. The VA has guaranteed a total of 32,760 loans on mobile homes since 1971.

Holland and Lyons Associates Inc., based in the District, has opened a Virginia office at Lee Highway and Blake Lane northeast of Fairfax Circle. Headed by Ron Zazzara, it will concentrate initially on residential and commercial brokerage.