The problem with buying any RV is that there is always the possibility that things can go wrong. A new RV comes with a warranty but just imagine what that warranty will cost you if something breaks when you are 1000 miles away from home and you are do back at work in a few days.
Buying a used high end RV may be good advice, if nothing major breaks. The thing is that unless you do a very very thorough inspection of EVERYTHING you have no way of telling what may break next week or next month.
Most people buy an RV based on what it looks like and how clean it is. This is a great way to get in to trouble because underneath all of the glitz is a very complicated drive train that if it was not properly maintained, can be very costly to repair. A neglected radiator can easily cost $5000.
Some people keep the interior spotless and only service the chassis when something breaks. This type of coach can end up being a money pit. Others are very anal about routine maintenance and their coach may last forever but there may also be an odor inside from their pets.
You also have to decide what you will settle with on a used coach. Do you want to sleep on a mattress used by others or is that something you will want to change before your first trip? A new mattress for an RV may cost $1000.
The truth is there is no guaranty when it comes to how much ANY RV will cost you next year of even next month. RV's are meant to be used and they are meant to be used away from home. This means that when something does break, you will either have to fix it yourself, or pay a total stranger to fix it. In the meantime, what do you or your family doing while the coach is broken.
It is false to think that a diesel coach will last longer than a gas coach. Both can and do break and repairs can ruin a trip and hurt the pocketbook.
If you decide on a used coach, spend the money for a very thorough inspection of EVERYTHING. This helps to identify obvious problems, but it does not guaranty that nothing will break on your first trip. If you need a little more protection to your wallet, you might invest big bucks($1500-$5000) for an extended warranty, that MAY protect you from catastrophic repair bills. Keeping in mind that most extended warranties have numerous exclusions when it comes to a used coach, depending on the age.
There is no easy answer and in fact buying any RV is a gamble. You have to decide if the gamble is worth the rewards. Most everyone on this forum have accepted the risks and are enjoying their RV. A few have been hit with very expensive repairs that have hurt the pocketbook.