If you really want to prohibit high prices, you can set a cap on rent per area and enforce with auditing. More typically, you limit the amount of rent increase

If you really want to prohibit high prices, you can set a cap on rent per area and enforce with auditing. More typically, you limit the amount of rent increases for new tenants, and have the original reference for rent be set before the law was brought up, so nobody had time to preemptively raise rent to cover rent control.