1st time RV project?

I don't know your friends skills.

couple of things that will make a big difference in the answer, does he have a place to work on it? If in an area with 4 seasons preferably enclosed and heated. Has he ever tackled projects that make up the different areas, cabinet making, upholstery, plumbing etc? The one in your link should be drive system solid but even the present owner states it needs a refresh of the interior and with the curved walls and ceiling everything will be custom made which equates to time and dollars. Thirdly does he have the patience this could easily take a year or more depending on time available and $$ available.

It's his money, let him spend it any way he wants. If the RV he is considering is in the same shape or better shape than the one in your link, he's getting a real gem. There won't be much to fix or change. If the one he is considering is a pile of nuts and bolts, it's still his money and if he wants to tackle such a project, why interfere! There are worse hobbies he could be spending his money on.