My only thought about leaving an A/C on during the hotter months in Texas, is the water or condensation that will pool beneath the bus in your nice new barn. And believe me there will be large puddles after a weeks stay on the floor of your barn under the bus, and when it starts running to the adjacent barns your neighbors may not like that?
I have not left the A/C's on during the first year in our storage barn, because of that. I had them install 50 amp service, just so I would have the proper power and everything has worked out great, other than my slide problems, but that is in another thread.
Gordon you will need at least a 14' x 14' x 50' accessible barn, so if he is willing to build that, tell him you will come ( I mean rent it from him) !
Gary S.