I have a 97 bounder 88k miles and been to the Playa 12 years... 460 food chassie with all the "Banks" add ons .. Gas RVs tend to run hot while idling for long times. So no big surprise there.
I'm the worry over Tires guy.. I never let mine past 4-5 year past the date code stamped on the sidewalls.. Front get move to the back @ yr 2 and fresh on the front. You'll never wear out tires but the sidewall go and blows outs are just not fun. New tires and maybe a radiator flush and your good to go.. Oh, tarp the beast every winter with a GOOD tarp.. rain rain wind wind....
LOL, I have an 89' Bounder about 56k miles.
The engine got cracked at about 44k miles, so the engine only has like 12k miles on it.
I know with my 22 year old RV, early spring maintenance is a must. And I'm not even talking winterizing. I would advise storing it someplace where you can work on it. RV's require a lot of easy DIY maintenance, that you don't want to pay someone Labor to do. On that note, if you'll be paying out for all the maintenance keep in mind that a few 100 a year will not be enough.
On this trip, our gas tank started to leak. It leaks where it rubs on the support straps. Its the original gas tank because it has the original asphalt/asbestos spray on fireproofing. Its a 90 gallon tank sitting on three support straps, where it meets the middle supports strap has started leaking. I was able to fix the leaks that would slowly drip before we left Fernley. At some point after Winnemuca, NV a good pin sized hole had developed. Long story short, I finally got is plugged and sealed for good, but we need to replace the gas tank before we get a leak I can't easily fix. I've looked into it, since that exact gas tank isn't in production anymore, I can have one made by the original manufacturer for about $350 bucks or I can have one made here in Denver by any old sheet steel house, or I can find a used salvage tank, or I can rig up a gas tank from some other RV. In any case, I'm looking at anywhere from $150 (salvaged tank from random RV) to $350+Freight for a spec brand new tank.
If you're mechanical, or even if you're not mechanical yet, owning an RV is a huge task. But, it can also be a great hobby. Old RV's are a lot of work, but if you like figuring out how things work, getting the parts and figuring out how to fix it, then sitting back and watching it work, its a blast!
Regarding the "over heat when stopped/idling" we had a similar issue on the way to the burn this year. Turned out to be the Fan Clutch on the engine fan. Once I knew what it was I was able to set to work fixing it. Wasn't difficult to fix, but if I had paid someone to do it, I would have gotten hit with 3 hours labor to install a $60 part. Typical labor cost is about $90/hr, $120/hr if they know they got you by the balls. Anyway, check the fan clutch on it when you go out to test drive it. Open up the dog house, and if the fan spins really easy, order a new Fan Clutch. If the fan spins, but has resistance then its not the Fan Clutch. I've also seen a guy with an old Winnebago that had installed an extra radiator and pump under his RV. It was near the back of the RV by the gas tank, seemed like more trouble and possible risk than it was worth though.
Don't take this the wrong way but, You would be stupid to not at least go test drive it.
A little more food for thought:
Chevy Chassis parts are easy to get (except Sundays and Labor day)
Ask exactly how much is "Large capacity grey and fresh water". Anything less than 25 gallons gray is small, 25-35 is average, and 45 or more is large.