A course in basic residential repair work will be offered Thursday evenings from May 8 to June 26 at Glen Echo Park in Maryland. For information, call 492-6282.

Condominium sales increased by 71 percent in the District during the first three months of this year compared with the same period last year, the realty publishing firm, Rufus S. Lusk & Son Inc., reported. Condo sales now make up 41 percent of the residential market in the city. Because condomimiums sell for a lower average price than houses, the total dollar volume of sales declined 16 percent in the first quarter of this year, Lusk said.

The Veterans Administration has created a single-rate interest for loans on mobile homes on their own lots, instead of having one rate for the lot and another for the home. The VA rate recently was increased to 17 percent for the combination loan. Interest rates on mobile homes without lots are now 17 1/2 percent.

Realty World, based in Annandale, has announced sale of its franchise rights in the United Kingdom to John J. Collins, a London insurance executive. William L. Janeski, president of Realty World, said that Collins has purchased rights to sell Realty World broker franchises in England, Scotland, Wales and Ireland. Janeski said this if the first successful effort by a U.S. franchise organization to set up an organization overseas. The five-year-old Realty World organization now has 2,000 affiliated independent brokers in the U.S.

Montgomery County's Housing Opportunities Commission plans to sell $25 million of tax-emempt bonds for low-interest mortgage loans to moderate-income buyers of new homes. A previous bond issue provided loans for 1,300 households. The second bond issue is expected to finance 450 loans for homes costing $65,000 or less.

Spaulding and Slye Corp. of Rockville has completed a survey showing that there are office projects totalling 1.7 million square feet planned or under way in Montgomery County.About 610,000 square feet of additional office space is rented in the county each year. The vacancy rate in the county is 5 1/2 percent.

Panorama Real Estate Inc. has named Howard Putnam director of property management.

David Baebler, a biomedial engineering student at Catholic University, has won the 1980 Robert W. Cotton memorial scholarship competition sponsored by the Consulting Engineers Council. Baebler, a native of St. Louis who serves as an intern in the office of Rep. Richard Gephardt (D-Mo.), ranks among the top five of his class of 100 students.

A three-day conference sponsored by the National Low Income Housing Conference continues today and Sunday with meetings at the Shoreham. The conference winds up Sunday with a luncheon at which former Sen. Edward Brooke (R-Mass.) will be the speaker. He is conference chairman.

Century 21/Singleton Realtors in Falls Church is sponsoring a free seminar for home buyers next Saturday. Reservations may be made at 533-7878. s