An old diesel with a 5.9 cummins or a DD in it will outlast your time. We gave people buying early 90s Foretravels for in the 20s and the run great and they full time in them. All coaches the age you are looking at of the older variety will depend on previous maintenance. I have friend in a 93 that are going to Alaska this summer. It is a small learning curve to go diesel but the older gasses usually will need a transmission much sooner if it has any miles on it. The newer gas units with a newer transmission us tougher it seems.