They were probably talking about Thousand Trails or one of the other clubs. You can try Thousand Trails by buying a pass -
http://www.thousandtrails.com/membership-info If you decide on a full membership buy a "used" membership and save a lot of money.
But first you have to decide what you want out of fulltiming. There are so many ways to do this. Some people spend months at one place then move to another, going back to the same spots year after year. Some stay for just a week before moving. Some only stay at resorts, some boondock in the desert and mountains.
Your style of fulltiming will figure into your budget and the type and size of RV that you'll need.