honestly with the way the economy is, id say you should wait a little while. It will be **** hard to get a good loan to get everything started and will cause major aggravation. You should get a good job and maybe do some stuff on the side in a garage, and save up your money.
Also, if i were to start a shop, the best way to go is to, even if your products are marked up, do really really good work. The better it works the more people will come by word of mouth, and most of the shops around me are ridiculously expensive and get everything done as fast as possible. One of my friends had this weird sound coming from his subs so i took everything apart, Car Toyz ran the RCA's speaker and power wire all on the same side, major interference. You would expect more from a place that charges so much you know.