When I purchased my used 2003 Fleetwood Pace Arrow rv for my new rolling home, I knew from research that things can and will go wrong. Just like any other home, there is the potential for systems to have problems. And an RV has LOTS of different systems:
Electrical system (for the vehicle portion)
Electrical system and batteries (for the house portion)
Hot water heater
Air conditioning units (2 on most rv's my size)
Refrigerator (electric and propane functions)
Rear and side cameras, wired to the screen of the dash stereo
The roof and all its sealed edges
Seals around the slide outs
The slide out motors themselves
and on and on and on.
All these can potentially have problems. Not every issue will be covered by an extended warranty, such as things considered regular maintenance or wear and tear, but most standard operations and functions will be.
My warranty was about $3200 for 3 years. This can be extended further at any time if I wish. I purchased it from the dealer and they were able to roll this into my financing so my monthly loan payment includes this amount.
Personal, I find great piece of mind in having this warranty on my coach... which is my HOME. Since buying the coach last may I've had recurring and ongoing issues with the brand new on-demand hot water unit I had the dealer install when I purchased it. (Repairs so far have been under my warranty, but they are now trying to work with the manufacturer to replace the entire unit under it's own 2 year warranty.) I've had 2 repairs to the heater/furnace unit. I've had to replace the seal around the bedroom slide. I've had the coach services for lube/oil/filter/coolant, etc. Not all of these fell under the warranty I purchased, but lots of it did. Even with a $200 per incident deductible, I'm very glad I've had it. In less than a year I've probably already recoup'd 1/3 of the warranty cost. I certainly wouldn't want something major happen that costs thousands of dollars and leave me without my home in a livable state. So I certainly recommend going for the warranty, especially when buying a used coach.
Also make sure you have adequate rv insurance as well in case of accident, etc. Make sure it covers the cost of your personal possessions. Make sure it will pay out full reimbursement for the cost of your coach (this is often an extra you have to ask for!). Make sure it includes towing! Towing a big coach like mine costs ALOT. You want that to be covered. There's no spare tire you can put on yourself on a coach like this. So towing coverage is a must!
Lastly, remember to BUDGET for maintenance and repairs. If you are considering full time rv'ing there WILL be expenses every year to maintain your rv properly, and there WILL be repairs. Even with a warranty some of those expenses fall to you. Be prepared!