Buying a house and renting an apartment represent only two of the possible living arrangements available, and these can both be cost-prohibitive. Co-op housing provides an alternative to the traditional methods of acquiring a primary residence. A housing cooperative or "co-op" is a type of residential housing option that is actually a cooperative whereby the owners do not own their units outright. Instead, each resident is a shareholder in the cooperative based in part on the relative size of the unit that they live in.