yeah, how much are you paying? have you paid for it yet? what's the mileage on the motor? lastly, what's the 'pricey repair issue'?
it's important to realize that when it comes to school buses (much like sailboats) it's a buyers market. meaning that there's way more buses trying to be sold than people buying them. so you as the buyer have most of the power. you can afford to be picky, so my first advice is to be patient. it's entirely likely that this isn't the bus for you.
for comparison, i got my school bus for $1,800. 116k on a cummins diesel engine, 35ft long with a rebuilt allison automatic transmission. now, i was extremely lucky, so on your litmus test of school buses, you're not going to get a better deal than that considering everything was perfect (tires, electronics, everything worked) and i didn't have to repair a single thing on it in over 2 years of driving it around the country.
now, the 'performance tours' logo on it makes me think this bus wasn't in a school district recently. the great thing about school buses, is that they carry children so parents, the department of transportation, and the state in general are all really paranoid about keeping their buses up to immaculate standards of maintenance. this is great, because if you buy a bus that's recently out of service, it's going to be in great shape and you'll go a long time without repairs.
unfortunately, i'm guessing this bus has already been running around as a tour bus after it's time as a school bus, so the mileage is probably going to be no less than 200,000 miles if you're lucky (more likely 250-300k). the cost goes way down after 200k. personally, i wouldn't pay more than $2,000 maximum on any bus with more than 200k in miles on it. if it has 300k, the price (for me) would go down to $1,000.
generally, if a bus is in perfect condition, and has not much more than 100,000 miles on it, i would be comfortable paying up to $5,000 for a full size (30-35 ft) bus. keep in mind that's the maximum price i would pay. if you pay any more than that on any bus, you're getting screwed.
i really can't reiterate enough how insane of a buyer's market it is for school buses. my dad is a teacher in washington, and they just sold their 2005 diesel short bus at auction for $1,000. it was a nice bus, in really good shape. there was only one bidder. the only reason i'm not rocking that shorty right now is cause my idiot dad forgot to put in my bid on it.
now, all this so far has been keeping in mind that the theoretical bus we're looking at is in mint condition. if the bus you're looking at is in need of some kind of major repair, then the price of the bus needs to be insanely cheap to justify the expense of the repair.
school buses, especially those larger than short buses are pretty difficult to get repaired in a shop. first, because if the damn thing isn't running in the first place, you need a special tow truck to get to the shop. even if you're working on it yourself, it's gonna be a pain cause it's basically a fucking semi-truck in smaller shell. so, if you're going to spend all this time and money on a school bus, it better damn well be in perfect shape right out the gate. there's no sense in cheating yourself just because it's right in front of you.
take a look around, call school districts, look on ebay, look on craigslist, and make sure to look far and wide. you WILL find some unbelievable deals out there if for no other reason than no one else is looking to buy what you're looking to buy.