You can read about 10,000 replies on this forum and still not find good recipe.
Usually coach defects are easy to fix and most of the time you can delay the repair.
What you want to research what coach in your price range has the most reliable engine and transmission combo. It is not going to be easy.
I just sold 44 old Prevost in perfect working condition (Ok it did drip ATF from time to time) what made new owners very happy, but even new Prevost can break down and having it repaired can take long time.
Bottom line, marrying comfort of classA with reliability is going to be hard and your budget is not making it any easier.
Just buy what fits your needs and have backup transportation (toad)