$3000 is a lot for a short bus that has been sitting for 5 years. You can almost guarantee that you will need to put more work in it than a radiator repair after being stagnant for so long.
If its a Co Spec'ed bus, I'd consider it. It looks like a fairly sweet bus.
Use the repairs it would need as bargaining leverage and see what kind of deal could be had.
Sitting for 5 years the tires will be shot. That's about their normal life expectancy and sitting on the turf that long is not a good thing. Fuel may have jelled meaning a good flush is called for. If air brakes, they can rust in place. Quite a few things to be checked. Then there are those field mice that have moved in...