Sounds like an interesting retirement option. I wonder how they deal with water hook-ups in the winter. Winters in NJ can get pretty snowy and heating an RV can be very costly. For a balanced price year round, they must have it all figured out. $625 for renting an trailer and campsite and utilities, that's really not a bad deal at all.
Hope it works out OK for you! (But New Jersey????).... what the attraction there. I was stationed at Fort Monmouth, NJ when in the Army. If it wasn't for the buses that ran into New York City (no way was I driving to NYC), it was a pretty boring part of the country to be in. Maybe all NJ isn't like that.