This subject isn't exclusive to FGRV's but it may be especially important to the older travelers like me.
I was returning from a fairly tough trip to central California (with my 13' Scamp) and my back operation started acting up, Big Time. The OTC pain killers weren't helping and the serious pain drugs were clearly not a good idea while driving. (The tend to make me both cheerful and inattentive.)
I drove into Ellensburg, WA and about 5 PM and, on an impulse, pulled into the Kittitas Valley Hospital Emergency Room. The doctors there spent several hours deciding that my operation wasn't falling apart but that I needed a good nights rest aided by a serious drug like Oxycodone.
They asked where I was staying in town and I pointed to my Scamp
(Self Contained). He said "perfect" and that is where I slept the night away, in the hospital parking lot.
The next morning I got checked out again and drove on home quite comfortabily.
Had I felt the need for medical help earlier into the day, I would have gone into the front door and not bothered the folks in the ER.
When I got home and shared my adventure with other ageing RVer's I found my satisfactory experience was a fairly common one. One fellow's wife is not well but they still make their annual snow bird trips south in an RV. They very often the spend the nights in Hospital parking lots sometimes getting test and brief exams. They always make it a point to check in and explain the situation. They've never been turned down and are only charged when there is an real reason.
PS I've talked to several doctor friends of mine and they made the point that hospitals in smaller towns are probably greatfull for the chance to earn the fees. However, if there's no medical issue, you may want to try WalMart.