I can't recall ever knowing anyone who said, "We did it, and it was fantastic."
One of our former best camping pals is a small business owner in the trades, and when times got tough in '08 he started renting out his Class A. He said it was never the same.
Not only was it never available when he wanted to use it, but it kept getting trashed, over and over. The rental agency was always able to charge back the repairs and loss of use to the renters, and they always repaired the major items, there were little things that were never detected by the agency and it just wasn't ever right again.
He finally stopped renting it out and spent a bunch of time and money to put it back right, but his beloved RV kind of lost its mojo after that, and we haven't been able to get him to come back out on any good trips with us in years.
On the other hand...
Two of our kids went to university up in Wyoming, and the little town of Laramie never could quite keep up with the rush of college parents coming to visit at graduation. There was a mixup with the grad dates (graduating in May instead of later in the Winter semester), so we were way too late to get a room within a hundred miles of Laramie, so we flew up to Denver and rented a Class C south of town and then drove it up to Laramie and parked it outside of our kid's house and had an amazing time being that close to the house and all the friends, party, etc.
The Class C was plated in New York and I asked the rental agency about it. They said that the owners would fly out once or twice a year to use their RV and travel around the Rockies, and then they would park it and rent it out the rest of the year. It was in good enough shape for our use, but it didn't have anything in it (bare bones dishes, etc.). We didn't cook in it, but we had to scramble to find some bedding to sleep in it. It suited our needs as a small mobile motel room. We would have had to bring all our own gear if we were camping, but I suppose that's fair enough.
So from my observations, if your friends intend to use their trailer very much for themselves, then they're not going to be very happy. But if they only want to use it once or twice a year and don't need to keep it very homey for themselves, then they might be able to make it work. It will never really be "theirs" though. It's more of a tax deduction than a useable RV.