I will echo the feelings of the others: way too much money for too many miles. And if that AT545 is the original unit, RUN away. These are basically 150k mile transmissions... maybe 200k with lots and lots of love.
There are some good busses to be had in Texas (but stay 100 miles away from border zones) and in Colorado. Calif has some deals too.
I wouldnt even consider a Florida bus. Sorry... Just the way I'm wired.
Your best bet is a bus from a school district in a relatively affluent and growing area, fresh out of service, and with service records. Ignore things like cracked glass, condition of seats, heaters, etc. Concentrate on engine, trans, and mileage. Lots of good, solid busses around the 165k mile mark, DT466e, and an AT545 or MT653 trans for about $3500. These are the workhorse busses from yesteryear that are being auctioned not because they are worn-out, but because the district has a policy set by their lawyers and beancounters, and there are federal programs to allow new purchases of "cleaner, safer" busses.
For the record, a DT466 with 150k miles is just getting broken-in. Yep, you will replace the occasional injectors, alternators, maybe an injection pump, the fan clutch, water pump, etc, but the guts are likely still within factory new spec: piston rings, bearings, valve guides.... all the expensive stuff is still totally bueno. Basically this is a late-teens or early 20's human. But by 350k, you are looking at a 50+ year old, and things are going to be a bit warn. It will leak a bit (or a lot), use oil, and likely need to hit the bathroom in the middle of the night.
Now compare this with the T444 you are considering. That motor runs hotter, turns faster, and is of a totally different design mindset. While the 444 is certainly no slouch, it also is designed to be a "throwaway" motor toma certain degree. So as a W.A.G I'd say its firmly "middle-aged" by the time it hits 200k (assuming good preventative care).
So like the others, I suggest you let the current bus go to someone else. There are better bargains out there.
I'll post a bit more after I change my Depends. Brb... Hehehe