Prebuilt portable garage shed?

Thanks for all of the advice given. I just thought that I would give an update. I ended up going with the 14x28 metal shed. I did have them add another layer of 5/8 flooring on top of the 3/4 treated plywood floor. I put the car in it today for the winter and everything seemed fine. Next summer I am hoping to run power to it and put osb on the inside walls.