Co-op bylaws are often written to encourage owner occupancy and preserve value for all shareholders. Understanding the nature of a co-op unit as a home, most co-op documents have provisions that allow for guests of shareholders to stay for a certain period of time, commonly up to one month, provided that the shareholder is also occupying the apartment.
It gets a little trickier if a “guest” is staying in a particular unit and the lawful residents of the apartment are not there with them. According to New York law, a “guest,” is not the same as a “roommate.” However, unlike many other tenant protection laws, New York Real Property Law Section 235-f, the “Roommate Law,” applies to co-ops, but the tenant must occupy the unit as well. Even if your guest has co-op approval, if you are not residing in the unit with them, the situation could actually be construed as an illegal sublet. No co-op wants that kind of negative attention. Indeed, if you fail to get co-op approval, depending on your co-op’s by-laws, the restrictions and penalties can be much more severe.
Subletting your apartment (legally) may also be difficult. In most co-ops, you can’t sublet your apartment without the board approval. Thanks to the business judgment rule, the board has wide latitude in granting or withholding consent.