I know the Catholic church runs retreats with doctors and other professionals on site for people with serious illnesses. There is a small fee which is waived if needs be. Those are not budget busters.
But you're right -- there should be a way to get away. I do remember, though, when I was really ill, I didn't want to go anywhere, or be sociable, just wanted to be quietly at home to read, watch movies, eat what I could without fuss, without dressing up. It's a toss up, there are a lot of expensive "facilities" compared to what I feel the market actually is.
Good luck with your projects, and congratulations on your initiative and on your resourcefulness. You'll think of something...
XOXOX
MaryAnn