Dave,
AFAIK the only place where you can legally and officially live aboard in NYC is the 72nd Street Marina on the west side. Anyplace else, you need a wink and a nod and to stay very much off the official radar. In the summer "I'm not living aboard I'm just spending lots of time on the boat" can often fly. Most marinas are not insured for "residential" use and they're afraid of someone slipping off the icy docks and drowning in winter, which happens.