My advice is to build in the most insulation, the best windows, and the most efficient house you can. Some will say it's a waste of money but, prices of heating and cooling are only going to go up. You will be happy someday when you have the smaller bills and still have money left over to go RVing.
I think I would build a SIP house myself. (Structurally Insulated Panels) Then I would add a 2 car garage and also a SIP shop in the back yard big enough to put the RV in.
My brother has pipes in the floor of his shop with hot water running through them from his outdoor corn burner for heat. Boy, is that nice!! Might be overkill where you live though.