so I was asking State Farm...
...even though I dont have a bus yet and just thought what I was told several times so far.
The biggest thing is that it's titled as an RV obviously, they dont insure busses as busses, even for private use.
The next biggest thing was I was told "electric only" meaning no propane, no fuel oil, no woodburning furnaces, water heaters, or appliances even a hot plate. I guess the reason is they are really leery of the fire risk with anything home installed involving burnables. Electric range and stove poorly wired by an amateur to 240 volts with a stack of paper from my office printer next to it is fine, but a propane RV fridge or furnace apparently is not. :P Apparently this isn't an absolutely hard rule, but it makes them look extra close and gives them extra reasons to deny or cancel in the future if you work with someone else apparently. Maybe if it's professionally installed with proof of it they will view it differently, i'll try to find out more.
I'm glad I asked early, I may have to plan electric only at least for anything permanently installed, or alternately to look at other RV insurance providers like Good Sam. (never called, just see the ad endlessly in Motor Home magazine, but dont know if they do homebrews)