July 22, 1984

BUYERS looking for a creative way to buy themselves shelter in New York City often consider purchasing a small rental building. The object is to obtain an apartment or two for oneself while counting on the rent from other apartments to cover all or most of the building's costs. The depreciation allowance permitted on the rental portion of the building acts as a tax shelter. Owner-occupied buildings with 6 to 10 units are being sold for less than $200,000 in the Bay Ridge section of Brooklyn and in Jackson Heights and Corona, Queens, brokers report. Prices vary depending on condition, cash flow and location.

Early in September the ''gift box'' that has hidden Bergdorf Goodman's Fifth Avenue entrance since March is due to come off, revealing the results of a six-month facelift.

THE QUALITY OF MERCY Cambodia, Holocaust and Modern Conscience. By William Shawcross. 464 pp. New York: Simon & Schuster. $19.95. FROM late 1978 through 1980, Cambodia held center stage among the world's disaster areas. United States involvement from 1970 to 1975 in its civil war had been only a ''sideshow''; Khmer Rouge terror from 1975 to 1978 had not been ignored, but while it was at its height, it did not register significantly on the world's consciousness. What propelled Cambodia into the limelight was the outbreak of war between the Khmer Rouge (the name by which Cambodia's Communist revolutionaries were known) and their former allies, the Vietnamese Communists. As William Shawcross, the author of ''Sideshow: Kissinger, Nixon and the Destruction of Cambodia,'' writes in ''The Quality of Mercy,'' ''Massive abuse of human rights alone had failed to win worldwide attention in the way that open schism and warfare within the Communist bloc did.'' As a way of legitimizing its conquest of Cambodia, Vietnam and its Soviet bloc allies helped bring the world's attention to the atrocities committed by

NEW HAVEN BACK in the 1700's New Haven's harbor bustled with activity. Shops lined the waterfront, which ran right into the downtown area. People regularly worked there, shopped there, or just strolled past. Today the harbor no longer bustles. Instead, people often remark, it smells. Like the harbors of many other American cities, it has grown isolated from the center of town and the center of activity.

At this moment, the Goodman Theater of Chicago may be the most exciting theater in America. In the last six months, it has spawned and sent to New York both ''Glengarry Glen Ross,'' for which David Mamet won the Pulitzer Prize, and ''Hurlyburly,'' the David Rabe drama that must be considered a strong contender for the prize next year and meanwhile is one of the choicest tickets in Manhattan. Then there are the less tangible, more private measures of success. French television wants to interview Gregory Mosher, the Goodman's artistic director. Mark Medoff, the author of ''Children of a Lesser God,'' sends his new play to the Goodman, unsolicited. Marvin Hamlisch calls to see if the theater wants to stage his musical ''Jean Seberg.'' To invert the adage, everybody knows you when you're up and in.