Answer:
A shareholder (One who is in a cooperate business with another, in other words, a business partner-that form of business is called partnership.)
Step-by-step explanation:
A shareholder (or stockholder) is an individual or company including a corporation that legally owns shares of stock in a joint stock company
When buying into a cooperative, the purchaser becomes a shareholder in the corporation (business) by virtue of stock ownership and receives a proprietary lease to the apartment for the life of the corporation (or business).