If you really want to open a magic shop, visit some. Really. Learn what they carry besides magic. Some sell costumes. Some sell jokes and novelty items. Very few make it on magic, alone.
Besides all of that, though, you need, as many have pointed out, the skills of a great demonstrator. And you need an outgoing personality.
If you can find Al Cohen, spend some time with him. He was one of the most successful. And go to some of the former great shops, so you can see how important the right counterman is. Check out Magic, Inc, in Chicago and Tannen's in New York. Visit Denny Haney's place. The contrasts will astound you.
The skills of a demonstrator are different from the skills of a performer. A demonstrator will show the trick and make you believe that YOU can do it. A performer will show you the trick and make you believe it is impossible.