Powered trailer dolly instead of an RV garage?

Regarding the structure-did you look at the portable garages that are soft sided? Much cheaper, relatively easy to assemble, and might fit in your desired location. I have 2 (truck and 5er) and find they work well. I also don't think concrete is necessary if you want to cut the cost down-I have a 3/4in granite rock base and it stays dry.