Great tips.
I don't know about flat roof leaking my house is over 20 years old and has never leaked and our community is pretty much all flat roofs which is common construction out here. Gravel drive shouldn't be a problem as that is also the norm. Like mine is a chip seal with little rocks.
But yes, I will look into all that but there are a lot of RV barns in my little community so this should fit right in.
Site prep will mainly involve cutting down some trees and clearing brush. Any blade work should be minimal...mainly smoothing the site like I said it's almost perfectly flat. I doubt there is more than 1' grade change on this section of my lot.
However, we shall see as I'm sure there are some surprises lurking someplace.