A buyout, as sibling mentioned, could happen, but would likely not be enough to make up for losing your rent-controlled apartment. In SF, most apartment rentals are covered by rent control so you can more or less predict how much rent you'll be paying years into the future (the annual rent increases are capped by the city and though they are supposed to be tied to inflation the allowable rent increases are likely, practically speaking, less than the inflation rate (for example, looks like for the coming year the increase is capped at 1.7%)).