An apartment building or a group of dwellings owned by a corporation, the stockholders of which are the residents of the dwellings. It is operated for their benefit by their elected board of directors. In a cooperative, the corporation or association owns title to the real estate. A resident purchases stock in the corporation which entitles him to occupy a unit in the building or property owned by the cooperative. While the resident does not own his unit, he has an absolute right to occupy his unit for as long as he owns the stock.