Here's a data point for you.
We sold our '02 Georgetown 32' Class A in late December last. It sold for just under $25K. It had the Ford V-10. We bought it 4 years earlier from the original owners. It had 12,000 milies on it when we bought it and just under 18,000 when we sold it. We averaged between 7.5 and 8 mpg, travelling mainly the west coast and eastern WA and OR.
As Magilla said, budget for new tires and batteries. The original 01 Chassis build date tires were still on the rig when we bought it in 2010! A new set of 6 Toyos (for 19.5" rims) at Les Schwab were around $2200. It only had one house battery, which was pretty tired. There was room for a pair of batteries. Costco deep-cycle ones were about $80. We didn't dry camp, and the batteries never needed to be charged, other than what shore power provided. We never needed to change the chassis battery.
There's also a chance, depending on age, that you may have to replace the slide toppers. The people we bought the rig from had it parked outside their lake-front home with the slides deployed. The living room slide faced south and a year in the sun rotted out the topper. Replacing both the bedroom and living room toppers was about $800.
The other, smaller things to budget for are water hoses, a sewer hose and storage box, crockery, cutlery, pots & pans, a toaster, maybe a coffee maker and maybe a small barbecue. We initially got a Weber Q220, but it wouldn't go in the stowbin without taking the lid off, so we got a Q100 for the RV.
When we sold the RV, we donated much of the smaller gear to our local Soroptimist store, except for the BBQ.
I hope you find something that works for you. Occasionally, a couple of the grandkids came along with us, but we had them bring a tent for sleeping as we have 2 elderly Labradors than needed sleeping space in the RV. You might consider having the boys use a tent when Grandma aomes along.
