Wow! Your story is not unique believe me. My wife tomorrow starts radiation treatment for her third cancer, two breast cancer. This last round started with a mastectomy. Before that we discovered all the discs in her lower back are gone. Because of that we in 2018 sold our RV after 35 years. Luckily we bought a small house in rural Oregon before the giant spike in prices, so we are OK for now on social security. Sadly what your thinking probably is not a good idea. RVs are a depreciating asset. Buying a used motor home could wind up costing you way more in maintenance that your income. Insurance, parking fees, maintenance, gas etc is just plane expensive. Think about where you would stay when it breaks down and is in the shop for a week? If you blow up a motor or transmission do you have the 5K in reserve to get it fixed? 6 new MH tires alone could cost you 3000 dollars. Camp ground fees even long term could run 600 a month in mediocre parks.
Most full timers consider 2000 a month as minimum to get by, and at that many supplement their money by camp hosting for several months a year.
I personally think you might be better off buying a mfg home in a senior park someplace warm.