I also agree with Stalkingbear , it will be hard to keepup with the retail chains , they buy in such bulk , you can not beat there prices if you are a mom & pop type store. You need to specialize to give your self an edge over them. It will be hard ,but doable. Do your home work ,buy a Shot Gun news if you haven't already to see what kind of dealer prices are out there.
Getting an FFL is not what it used to be , expect a long procedure and they (BATF )will want a floor plan of you shop and times of business hours and a lot more .Good Luck , you will need it ,dealing with the ATF.