The answers below seem to assume that you already own a co-op and are asking about rules for subletting it. However, I am not entirely certain from your question if that is what you are asking, or if you are contemplating purchasing a co-op and would like to know the feasability of renting it out in the future.
Most co-ops are expected to be owner-occupied. Subletting is generally frowned upon. Therefore, each individual co-op board makes rules about subletting. The most common is you may do so 2 out of 5 years. It varies building to building. If you are considering a purchase and the ability to sublet is important, you may want to consider a condo instead. If you are just curious, ask your agent (and I certainly hope you are using a skilled buyer's agent) to find out the subletting rules for units you are considering.
Halstead Property, LLC
I can tell you one thing for certain though, the coop application process for prospective renters is often one that is long and tedious. Thus, many people tend to shy away from coops completely and either rent from condo owners or go to rental buildings.
Nick A. Agostinelli
Licensed Real Estate Salesperson
office 212.729.5712 EXT 144
353 Lexington Avenue, Fifth Floor
New York, NY 10016
Real Estate & Development