I came to this dance late, but after owning for a few decades here is my $.05
Rule #1: All RVs leak. Dont care who made them, how new they are. How much it cost. All RVs leak. The quarter-mil (and up) bus based coaches leak LESS, but, you paid a quarter-mil and up.
That being said, never go after the cheaper wooden space frame/fiberglass insulation/siding covered ones. They leak the most, have mold the most, come apart the easiest and are just cheap.
You want the aluminum framed ones built like a cooler, that use foam panels and have the fiberglass skin bonded on the outside. When they leak, the water stays to the outside - keeping the required repair work out there, and not the interior (mold!)
Do you want a TT (travel trailer) or MH (motorhome)?
If you want a motorhome, the LEAST trouble you will ever have is to get a 90+ Ford E350 cutaway based unit - the 460EFI and E4OD is failrly bulletproof, adult designed and will deliver what you need.
GM invented the 400SBC because the vans could not take a big block. If we are talking 22ft, the 350/400 versions are ADEQUATE. IF you never tow.
The 460 in my 29fter steps out right smartly and still gets 8mpg. Yes, they get 8mpg. The 4bbl versions with the C6 get WORSE.
Guys with the V10 do get 10, but far newer = more $$$
Avoid diesel from any maker but one - not worth the drama.
However, if you got some cash, the Winnie View (22-24ft) on the Sprinter 3500 chassis with the 5cyl benz diesel - 18-21mpg!! (step dad had one, just sold it for a bigger class A)
You gotta equip the interior based on where you will be. I have heat, AC, genset, full kitchen etc because we camp 8-9 months of the year and often boondock (no services)
Look for one where the owners were older and had no kids. Or pets. Kids drop stuff, pets pee. period.
Pay attention to towing if you are going to. My 29fter has an 8' overhang (or more) and is hence rated at 3500lbs with only a 300lb tongue. We do overload by pulling a dolly (500lbs) with my Jetta behind it. WE also tow a 3500lb carmate to the shows, the class A chassis and the newer E450+ chassis are reinforced to tow more.
The biggest pains in the a$$ are the plumbing systems and the control boards for appliances. If you or your mom cannot plumb in pex, you will be paying a LOT for stuff that breaks a lot. and the control boards seem to always fail. I am about to do the hot water the 2nd time, I replaced the fridge board and I did a complete replace on the onan emerald - control plus VR. Since I can do these things, it only cost me $100's, if you have to have someone drop an onan for you, its over $1000 just to start.
And then, the TIRES and brakes. Since they sit so long, the front calipers stick so damn often, you replace the entire front brake system every couple years. And lets face it, tires are out of sight. So people buy the new fad - korean tires. I have yet to see a set of korean 'truck' tires (they are all load range E) that do not break belts as soon as you get them rolling.
Find your best deal, check it out everywhere, ask questions and still prepare to spend a lot of money on the side.
ps: all but the most modern units use converters that charge the batteries at a 3-5amp rate. MAX. And all the incandescent bulbs inside draw at least an amp each. There are close to 20 bulbs on average in a unit. Your lights, will take you down. If you boondock, think 2 batteries, LED lights, and bypass the converter charger for a higher power multi channel unit (I use a NOCO 10 amp per channel charger and 2 group 24's)