I would highly recommend finding a partner that understands how business works, or taking some management classes BEFORE you start down the road of opening your shop. The office portion of the business requires finesse.
Advertising, paperwork, point of sale receipts, warranty's, talking on the phone to schedule customers, order and run for parts. All these things should be done by other people. Taking time away from a repair to answer phones, or run and get parts is a waste of your time. Dealing with the office is a waste of your time, when fixing the cars is your part of the business, the thing you are able to do well.
It is also more economic to have multiple mechanics under one roof with a team handing the paperwork, the parts, etc than to try to do it all yourself. With all the legal, finances, paperwork, insurance, etc you'd be out of business before you got started.