I would dig into exactly what are they offering. What parks, what services, what discounts. If you have to pay just to get that information, it is likely a scam.
Many private RV parks not at high-traffic locations are in discount clubs like Passport America. There have been others, like Camping Club, but PA has been the survivor over the ten years I've been RVing. It is worthwhile if the locations and schedules work for you.
Still, I haven't joined. My late wife liked KOAs, which aren't really cheap, and where I live, I get the most value from town or county RV parks, or my senior pass discount at Corps of Engineers facilities. State parks come close for a few states where admission is free and seniorsget discounts, but for many states the park fees are as high as those of private RV parks in the area. Texas has reasonable camping fees but high per-person per-day fees. Other states have high per-vehicle per-day fees. Colorado even wanted a day use fee to use the restroom at a roadside park.
You can go all the way up to park membership and save money, if your pattern of use fits the program, but you shouldn't commit until you've had time to figure out how you will be RVing.