When you purchase a co-op, you must state exactly who will be living there in the co-op application. When you say they don't allow subletting, but you want to know if your son can live there, I get the impression you are talking about an adult son, and are wondering if you can move on and let him then live there. If you are purchasing it, your name will be on the proprietary lease, and whomever is on the proprietary lease is who has board permission to live there. I would be very cautious about being tricky about bending the rules, particularly since a board that allows no subletting is a very strict board compared to most.
I certainly hope you have a great agent working with you as well as a skilled real estate attorney. They should review bylaws, house rules and also get clear answers from the managing agent on whether what you are proposing is permissible.
depending on your and your son's particular circumstances, you can either own apartment jointly with your son, i.e. have both of your names on the stock certificate and on the proprietary lease or can just add him to the proprietary lease. It should be specified in your board application who will be living with you in the apartment and at the closing, your attorney has to make sure the lease includes your son's name.
Some coops may want to run a credit check on him, as well (not sure what age he is) and will ask him for an interview...some coops will even want to have a full board application with his pay stubs, taxes and bank statements (again if he is an adult).
You should discuss all possible options and this coop's requirements with your attorney and a broker, if you have one. I would be happy to assist.
646 593 7207