If the rig is close to 10 years old, it is time to re-seal the roof. That is a big ticket item if you have it done. You can DIY for less than $100 with Eternabond.
Tires need to be replaced about every five years. That will cost around $1600.
You should get a car fax report and maintenance records.
Check under the over-cab mattress for signs of a leak or dampness. That is an often-overlooked point of leaks and damage.
Does the AC cool? Does the furnace heat? Water heater? Water pump? Does the refer and freezer desired temps? [less than 40 and less than 15]
How are the coach and engine batteries? Do they need replacement?
Check the hours on the generator. There should be one hour for every month since it left the factory. Don't be upset if there is more than that.
Use the LD owners manual as a guide/checklist of inspecting a used LD. Just start with the index and work your way through until everything is covered.
"DON'T buy on impulse". Get a mechanic to check out the drive train and suspension - engine, transmission, bearings, springs, shocks, steering linkages, battery, etc. Get an RV tech to check out the coach and its systems - electric, water, propane, heating, cooling, leaks, structural integrity, window seals, and so on.
The other big issue is "What should I pay for it?" Barry Barnes does an annual analysis of asking prices which offers some guidance on prices of used LD's all the way back to 1963. You can find Barry's analysis on WxToad's site.
Contributors: Delta Mike, Barry Barnes
Revised: 26 Nov 11