I'm assuming you're leaving Mexico
I know RockNRuth have offered their property to those who need a place to do their conversion. Maybe they would be open to storing your bus??
Per having it under cover, here in WA, I simply covered mine with a good tarp to keep it protected from the weather (rain mostly, but a bit of snow too). I was actually very impressed with how well it worked.
The tarp draped down past the windows, and then I would open a couple of windows just a bit to allow some fresh air during warm weather, even when it rained.