It is like many other businesses. It is all about creating enough volume to make a living off of. Know who the potential customers are in your area. Then estimate a small percentage of say 2%. This could give you a rough estimate. Good Luck!

im trying to start a business and its kind of odd installing door strikers $75 a door do i need a license and do you think this is a profitable idea?(door strikers are extra protection from intruders trying to kick down your door?