If they don't know RV then they will break something.
I used to buy and sell one RV/camper per year. Everytime, sorry wives, the wife would come in and pull or yank on a cabinet door that had a safety latch. I got to expect it and prevent it, but it took several broken latches to learn that people just think they can yank, pull, and generally terrorize the RV if it does not work like they think it should, not knowing it is latched for driving or other peculiar things you find in an RV... Guys do the same, but the women always try to operate things without getting instructions...
There is a whole lot to communicate to your friend on how to operate an RV, it will overwhelm them possibly... dont park off-level without turning off the fridge, dont do this... dont do that... Yes, you are risking them unknowingly breaking stuff.
That said, I know people who do rent, and you just charge enough to cover the expected damage.
Here is one for example, Im not advertising anything, but this gives you an idea of what they charge and how it all works on the professional side.
RV Rental AlabamaThere are many others you can do a non-google internet search for and find. Seems there are companies that can handle the rental for you, similar to renting a vacation cabin....
I dont loan my RV out. I let a family member take a C out and it came back a mess