Considering converting cargo trailer to RV - need advice

Have a friend who has converted her camper shell to a small living space that is fine for her. Trouble is, she is now finding lots of park will not allow her to stay there as she is not self-contained. She can sometimes stay in a tent area but would like to stay where she can have electricity to watch her TV. Struggling to figure out what she can and cannot do. Just be aware of possible restrictions on converted trailers/vans/trucks in many parks.