You need a good reputation as a builder/restorer if you want anyone to trust you with their high dollar investment. I would do it as a side business to get the ness. experience and reputation. Are there allot of muscle car owners in your area? Enough to keep you busy and are they willing to pay what you need to stay in business? Do you know how much you'll have to invest in tools / parts / building / etc. to start up a muscle car shop? Many questions come to mind, but these are a few starters.