Take the time to find a good reputable diesel shop that knows busses & is licensed to perform DOT checks for commercial vehicles. I have had my CDL for about 15 years (class B) & every vehicle I drove had to pass routine DOT checks to be legal for the road. It will cost $125-$150 to have the check done (at least where I am) but this way you will know what the bus needs before buying as it is a thorough inspection...My wife & I just bought an '89 Thomas Transit Liner & had the same inspection & it is good to know that there are only 2 minor mechanical issues I need to address as our first trip is going to be 2000+ miles - better to know now than finding out on the side of the road in the middle of knowhere (yes, it happened to us bringing the new bus home).
Just a thought!