As stated Coast 2 Coast and RPI (And a few others) are all basicall "Exchange" services, You buy a membership in a campground (Thousands of dollars plus a lifetime of dues payments) and then for a heavily discounted fee (I think 13 bucks a night at most parks but have not used either for a few years) you are supposed to be treated just like a member.. Some of them do it, some klind of violate that rule (I have, for example, been assigned parking in an ared "Reserved for Coast 2 Coast" most parks would call it "overflow".
Howver if you'd like to TRY membership camping without the lifetime dues thing.. I have a deal for you. PM me for some iformaiton but basically it's Thousand Trails.
They no longer sell the lifetime memberships far as I know.
They sell an annual "Zone pass" each zone (about 1/4 of their parks) is seperate, you get one zone for about 500 bucks, You get a 2nd zone for a bit more. One year, you can renew IF YOU WISH, 500 is about what some parks charge for dues.
Home is where I park it!