I got a estimate for a 2x6 stud, 20x40 with 14x12 foot door, man door and four windows. Stucco exterior, unfinished inside no electrical (I was going to do it myself) for $31,000 including the slab. I did not want to spend that much so I had the slab poured with footings should I ever decide to build a stick and mortar shop on it.
My guess for a shop like your describing around 30x40,x14 with two doors, finished inside and out with electrical would be in the $50,000 to $75,000 range..
You might not be able to go this route, I went with a metal RV port. 20x41 sides are 9' center is 12'. No real snow load here but had to have permit and engineering specs to show wind rating over 110mph which I got from the installer for free.. Total cost including RV Port, installation, slab and some sidewalks was $11,000
You can enclose it, make it taller, shorter, bigger, roll up doors. Just depends on how much you want to spend..
