Another rule of thumb is that you can expect to spend 10% of the purchase price the first year putting things "right". There is probably some deferred maintenance and small things inoperative that you'll want to get fixed. The first year I owner the Sahara, we replace both TVs and fixed a bunch of little stuff.
IMO, the key to owning an older coach is doing most of the work yourself. I make an attempt to fix everything that breaks. If I can't figure it out, then I take it in. The last thing that "broke" was the inverter. I diagnosed it as a cabling problem, the shop said it was a bad inverter (2 year old Magnum). After installing 2 new inverters, they finally found a bad ground.
My fridge wasn't working on gas. After the above, I decided to figure it out myself and spent $60 in parts (new burner assy and a piece of tubing) to fix it. I'm sure the shop would have tried to sell me a new fridge or cooling unit.
The only thing I don't do myself is an oil change, only because it's a PITA to dispose of the oil.