Building a garage, cost $$$$
I am a sales manager for a building manufacturer and will tell you from experience the first thing that you need to do is contact your local building/planning authority because some types of building contruction are not allowed depending on local codes or covenants. For example, pole buildings and/or steel siding are sometimes not allowed. You don't want to find something that fits your budget and then you find out it is not allowed so now you are at page 1 all over again. If you decide to purchase a structure via the internet don't rely on the building seller to tell you that it is allowed. I have also seen buildings sold to people that they weren't allowed to erect so they were stuck with a structure they couldn''t use. We as car guys see fly-by-night suppliers all the time and will tell you that the same is true for building manufacturers, just more dollars at stake.
Chuck