RV resident parks such as you seek are common in Florida, the Carolina coasts, Arizona, south Texas, and along the Gulf Coast of Alabama. Most are the type where you purchase your site as a share of the park, but there are often sites available for lease or rent as well. There will also be some commercial RV parks that offer annual site leases. Amenities & prices can vary anywhere from luxury to trailer trash.
I suggest you try to narrow down where you would prefer to live, taking into account cost of living, climate, availability of health & medical facilities, any family connections you want to maintain, and your preferred RV lift style. Visit as many such places as you can rather than relying on second hand descriptions or internet reputation.
Google long term RV parks to find them.