Sounds like they are thinking of a motorhome. I've met a number of singles (and couples) full-timing in small C motorhomes (24-foot and under) or type B van conversions (which can be 17 to 24 feet long and no wider than the maximum for a "standard" motor vehicle in the U.S.). The latter can be quite drivable, my daily driver and road trip vehicle is an 18 foot passenger van.
What is needed is to scale one's lifestyle down to the space available. I can do this myself for part-timing, but cannot for full-timing, as it means discarding the remnants of my life with my late wife, and all the stuff my children presume that I am keeping for them until they want to take it (probably not until I die).
As I'm not a full timer, I can't tell about dealing with the full-timing issues, except to say that they have to be dealt with. One cannot be "stateless" in the U.S., a domicile state is presumed, and if that is not to be left to chance, it must be formally established.
Escapees has a lot of the answers. They can provide a domicile and handle your mail.
Prescription medicines can be one of the tougher problems, particularly if the drugs are controlled substances, or require periodic monitoring for adverse side effects. But there is the larger problem of getting medical care, once you are separated from your physicians; we do not have a national health care network where one can walk in any place and the care givers know all about you.
This is another of the issues that keeps me at a home base from which I do my traveling, a mix of RVing, road tripping without RV, cruising and globe trotting that keeps me away as much as half of each year. I had to build a new relationship with care providers when the one I had for 20 years retired, and I am in no hurry to start over again or put myself into the hands of random strangers.
