Most CO-OPS have very strict policies about subletting, which does not make them an ideal investment opportunity and can present a serious challenge if your job suddenly relocates to London, for instance. The rules vary, but owners are usually allowed to sublet their apartment for no longer than 1 to 2 years in any 5-7 year period. The board also gets to approve your tenant and charge you a fee for subletting.
CONDO sublet policies are far more liberal. While there may be rules against short-term sublets (say, less than 6 months), there is usually no outside limit nor do boards have the right to turn down a tenant unless they exercise that right of first refusal and lease your apartment themselves. But just like a co-op, the application fees, move-in fees, processing fees, etc., can range from a few hundred to a couple of thousand dollars extra that you or your potential tenant will have to pay. And you will be living in a building with a more transient population than a co-op.