My step-brother and his wife lived in an RV for a few months a couple of years ago. They are not retired, but brother is on disability and wife had lost her job, and they had their D C pregnant daughter, hubby, and several grandchildren move in with them and they were at the end of their rope. They sold everything they owned, bought a $2000 RV and a cheap car to pull behind it, and made a horrible deal on their house (did some ill-advised lease-to-own deal) and left.
There are websites dedicated to groups that live this lifestyle, and they have a lot of info on how to get jobs at a campsite in exchange for lot rent, etc. Sis was very excited about the whole thing. They lasted about a year and decided they wanted to move back to where they left, sold the RV car, and bought an SUV and went back. They are renting a small place in the backwoods on 500 acres from a friend.
I am interested to discover how little you really need to live. I wish I had the courage to get rid of even more stuff.
Back to retirement, my X and I planned to do this, with a piece of land to live on when we needed it. It seems very doable, at least until poor health requires you to be need doctors and such near at hand.
I have brought this up to hubby and it is a possibility for us, also.