Over the years, I have had at least two Coast to Coast memberships. They can be bought "used" for a couple of hundred dollars. Some of them, as mentioned, expect you to pay their dues forever unless you transfer it to someone else that will pay the dues, but there are others,(at least there used to be) that have some sort of exit clause that allows you just to quit. I think that generally those are in far away places that you will probably never visit. They actually count on never seeing you and just receiving the dues. The benefit of those is that you can use that national system, which is what we had wanted to do, without ever seeing the "home park". I do not know what is available these days though.
Ed, The alternate strategy is to pay for everything by credit card and pay the balance every month. Some of the rewards programs will give you back $20 per $1000 spent. It may not seem like much, but it does add up.