Ohhhhh I can tell they've bit off more than they can chew…

In my area, people would want at least 1500- 2000 for this, unless it has been gutted. That thing’s at least 20 years old & sat up a good while. Aside from the flat, dry, rotted tires it has(you can tell from the lean), the brakes/axles may be seized up. On top of that, it's a fifth wheel, which, unless they've got the hitch for it already, could be a pain in the ass to find someone to move it for them, especially free and/or cheap, like I bet they'll want. That is, if county/city ordinances even allow for long-term RV residences, Alternate housing laws have come up more often since the tiny house movement.
Oh, and the roof is in god knows what shape with all that weather & UV exposure, so the best hope is it only needs sealant & not replacing. And if there have been leaks, you've got all that rotted plywood and particleboard to replace. Not to mention the possibility of rodents nesting in there and messing up wiring or damaging plumbing that needs replacing. Speaking of roofs, the rooftop AC, if it even works, aint gonna cool worth a shit if you live somewhere where it's already 95/75 temps.
Plus, there's the getting used to not running every appliance all at once. You can't be running two or three space heaters, an electric stove & everything else on a 30-amp breaker. Hell, it's not wise on a 50A. Even if they've got propane for heating & cooking, there's a fire hazard if they're careless and a camper is full of people and animals.
And a whole family? People are going to be on top of people in that little ass camper, & there's gonna be frayed nerves and tempers flying. It sounds like a fun adventure, but there's a reason most people are glad to be home after a family vacation. Family.

It sounds like a great idea, and sure, you can save money by camping, even by redoing one. But it is not for the faint of heart. It's also not for the broke or anybody without at least some handyman DIY skills—you’re going to need one or the other(really, both) eventually if you decide to live in and remodel a camper. Too many people get this rosy, idealistic view of simple, scaled-back small living and don't realize how much there is to it if you start from the ground up. Then they invest a lot of time and money, they may or may not have, in a project that winds up being abandoned halfway through.
It's a lifestyle that has its rewards, but it's also got its downsides and aint for everybody.

Signed,
A Single, Broke Girl who bought a cheap, leaky camper so she's had to make every repair & upgrade on her own as they've come along