My suggestion is do a lot of research and clearly know what you want!
We joined a membership plan. Yes, it is a lot like a timeshare "investment" There is the upfront purchase and then quarterly fees.
Our RVing is traveling from place to place and sightseeing. NOT staying in 1 place for a long time.
We found that the RV parks were not close to where we wanted to be. We would have to go out of our way to use a park "in the program"
For example, We wanted to visit Jackson Hole. The nearest park was about 1 hour away. Not convenient.
Know what YO)U want and look at the details closely.
It MIGHT work for you.
Cheers,