There is camping at the club (I think $25 a night for two people), and a van is considered a car, while an RV is charged by the foot on the Ferry.
Also there are a lot of B&B on the island and homes available. Ours used to be, but we moved into the house.
Chamber of Commerce has a good list to choose from.
You can go to my PIB website where down toward the bottom I have a ton of links for all sorts of stuff:
http://www.catsailor.com/putinbay/house.html