You would do yourself and the next owner a favor by installing a 14ft high x 12ft door (14 or 16 would be better) in the largest building you can afford. In its lifetime the building can and will be used for many things. To me 10 acres equates to toys, lawnmowers, tractors and utility trailers. You only need to frame, side and roof it at this time. All the rest can come later, on your time and budget. A good concrete floor is a must have.
I have built many buildings in my lifetime and have regretted every pole barn style I have ever built. The largest being 96ft x 144ft with 14 ft doors. It is expensive to do anything with them, like insulating and covering the interior walls and ceiling. Plus it is darn near impossible to make them rodent proof. The last thing you want around your RV are a pack of cold and hungry field mice.
My father in law constructed a building for his motor home, 10 ft wide door 12ft wide building (outside dimensions) with no room front or back with the class A in it. A total disaster.
You cant even open the door and deploy the steps.