It would be fun to build a two stories recreational vehicle. And the amount of space there is!
But no garage for any size passanger vehicle. Sauna yes definatelly but you don't do groceries with double decker bus :) You need to have some kind of vehicle with you to make living especially winter time easier.
And as your "house" is married to the vehicle it is very important that you can get spare parts and repair services in any city it happens to break down. It would be virtually impossible to get local help here in Finland with the problems these beauties shall have. And repair services are expensive for heavy vehilces as they are ment and usually used by businesses that can subtrack the repair expenses in taxation of their business.
And they are ment for wrong side of traffic :)
First idea was a double decker bus