[350TacoZilla]

I doubt this will be popular advice but I'm use to money being tight so I would build the shop you can reasonably afford now but plan for an addition down the line. I love seeing the guys build 120'x120' dream shops with living quarters as much as the next guy but if you can get anything over maybe 30'x40' on the ground with concrete floor you have a good start, just place it where you can expand type of deal. That and make at least one side have an extra concrete parking pad incase you have something to work on outside that won't fit in the shop that you will eventually fill up.