A guy that I worked with retired recently and is now driving around the country with his wife in a camper-van. He and his wife were not sure if they would like it, so they rented a camper-van for a test vacation before he retired. They liked it enough to buy a van and have it converted with the camper add-ons.
The van is like your common delivery van with an extended height. It has a kitchen, bathroom with shower, bed, etc. He said the advantage of a camper-van is that they can park it pretty much anywhere a regular car can park. They figure they can camp at an RV park and use the hook-ups, then easily drive around the surrounding area to sight see. With an RV, they are pretty limited as to where they can park and sight seeing would be a chore without a normal sized car.