Well, the repair would obviously be a portion of the music store. Plus I am going to be prototyping Microphone casings for a joint venture between my dad (a sound technician) and my uncle, and electronics genius. But that is still months if not years away.
If you have family prepared to back you up, I say open a business. It'll be rough, especially at first, but with the right people and right planning, it can be quite successful.
Just avoid any towns with Guitar Centers!