Go surf the Honda/Nissan/Toyota forums on this site...

...You want that to be the client base you specialize in?

I think its a bad idea to just say, "I want to work on rice rockets". Most of your customers would be kids, many of who are dishonest little punks. At least to start out, Id' say work on anything you can get in the doors. One die hard car enthusiast, reguardless of what he drives, is worth more than 10 20-year-old rico suave ricers if you can get them to use your shop for all their car needs. I've seen it happen at mechanics' shops, sometimes even 5 or 10 cars from the same person being worked on. Its hard to get that kinda loyalty with the client base you're selecting.

And for the love of god, invest in good security. These punks are stealing the parts right out of performance shops these days.