Building a garage, cost $$$$
I built my 20 x 20, (that's all the county would allow), myself 4 years ago. 6 inch slab with huge footers and a driveway about 130 ft. long that wraps around the back to the shop. 8 foot walls. Again, that's all I could permit. Nice steep roof so that a lift is possible and I have a nice storage loft on one side. It is fully insulated, drywalled and air conditioned. Power on every wall. 100 Amp. service. TV cable, computer, alarm, phone and sprinkler system all wired in. Every nail, screw and tool included ran me $11,000.00 ... I hired a few guys to hang the ceiling drywall and help with the roof as I have a bad back. Also hired out all the concrete work. Again it was at a total cost of $11,000.00.
I had about 5 or 6 contractors give me estimates. $30K down to $11K. The $11K guy was just to dry it in and I had to buy all the materials.. I said screw it and built it myself. It took me a long time to do it all, but I have a bad back and sit more than work..
The biggest thing I can tell you is to make a great plan. You have to reallllly know where you want things and place what you need where it needs to be now. Later will make it a real pain in the ***..
You can never have too many lights or outlets.
Don't forget to wire in lights outside too...
Once you have a plan go over and over it. Go to your buddy's shops and ask them what they would do differently and what they really like about their shops. don't forget about heat and A/C.
I also buried a PVC (sch.40) pipe in the ground from the shop to my house garage for compressed air.
My only regret is that I didn't buy a place with a larger yard so that I could have built much bigger. Do your homework....