RENT CONTROL is scheduled to end in the District on Sept. 30. But it is unlikely that the law will die. Half a dozen proposals are now circulating that would give new life to rent control. But in considering ways to extend rent control, without first judging what effect it has had on the city, politicians and officials are avoiding a key question. It is: is rent control good for the city? And the answer is that it is not.

Since rent control came to the District in 1971, construction of apartment buildings has decreased. From 1974, when rent control became a permanent law, through last year, the city lost 12,600 out of about 180,000 apartment units, or about 6.7 percent, according to city housing officials. At the same time, condominium conversion and construction of condominiums have increased dramatically. About 12 percent of the city's rental housing stock has been converted to condominiums since 1970.

These occurrences are not unrelated to rent control. That program has limited revenues for apartment-building owners while doing nothing to limit inflation's effect on the cost of building maintenance, the cost of utlities (in particular, oil) and the value of apartment-building property. As a result, it is to the advantage of many landlords to get out of the business or to put their buildings to other purposes, such as condominiums, hotels or whatever else may be possible.

With more laws, the city government has tried to slow this trend. Thee are laws that limit condominium conversion and laws that limit what uses a building may be put to once it is no longer an apartment building. The result has been that some landlords are trapped with their money invested in apartment buildings that do not make money for them. Consequently, some small investors have been forced to abandon their buildings. Owners of large properties simply delay repairs and maintenance. The District government is occasionally drawn into the problem when landlords say they cannot afford to pay utility bills. In 1978, for example, the District government's housing department had to pay for emergency deliveries of heating oil to apartments for over 500 families because landlords failed to pay the bills.

Proponents of rent control say the statistics are deceptive. They claim that developers were not building apartments buildings before rent control went into effect, that most landlords are not abandoning buildings and that rent control has helped to stabilize the city because many poor people would otherwise be displaced by the wealthier people who are now deciding to live in the city.

These arguments are not convincing. It does not matter if developers were not building apartment buildings at a great rate when rent control went into effect. It does matter that they are not building them now when the need is great. Simillarly, rent control does not help the city when it is compelling apartment-building owners to let their properties deteriorate. And finally, rent control does not help poor people. It is a disincentive to construction of needed apartment buildings and to maintenance of existing ones, especially in poor neighborhoods.

Rent control does not do all that much to keep down the cost of apartments for the poor, either. About 20 percent of District residents were paying over a third of their income for rent in 1970, prior to rent control, and in 1977, while it was in full bloom, about 20 percent of District residents were still paying over a third of their income for rent, according to the U.S. Census Bureau. Poor people, as a class, are not better able to afford a place to live because of rent control.

There are some people who will need the city's help when rent control is ended. The elderly and low-income people may have trouble finding a place to live in the city until developers realize that in the absence of rent control they can make money by providing low-rent apartments that are located outside the currently popular neighborhoods near downtown. Until then, rent subsidies for the poor and elderly appear to be a good idea. But the best idea may be to offer tax incentives to developers to begin buidling apartment buildings throughout the city.

The main reason to keep rent control appears to be political: many people regard politicians who oppose it as enemies of the poor. What is needed now is for strong politicians to stand up to the myths surrounding rent control in the District and say no to extending this bad law.