Don't know if I qualify as an "old timer" but I'll throw my $0.02 in anyway.
You have definitely come to the right place to learn all things Skoolie. There are a bunch of very sharp folks here that are very generous with their time & knowledge.
The bus in the CL ad looks nice. Low mileage and underbody storage are big pluses.
I would question: Which Cummins engine? 5.9 or 8.3?
Which Allison transmission? AT-545, MT-643, MD-3060 or other?
That will make a big difference. If it has a 5.9 and AT-545 you wont win any races or climb any big hills. In that size bus I would have a strong preference for the larger motors (Cummins 8.3 or International DT466) and better transmissions. The Allison AT-545 is a 4 speed without a lockup torque converter. The MT-643 (or 647) is a 4 speed with a lockup torque converter. The MD-3060 is a 6 speed with double overdrive. Unfortunately, in buses, 6th gear is usually locked out leaving you with a 5 speed overdrive.
If that bus had the 8.3 & MD-3060 and is in good shape I would not hesitate.
Don't want to forget tires... Age & condition. Even with plenty of tread, tires die of "old age". A new set of tires can run you $1500 on up to whatever you want to spend.
Go take a look at it. Take some more pics and post. I am sure that you will get all of your questions answered.