It depends on what state you are in... some require one while others do not. The scale of your sales might also be a factor (as in if you sell over $$$$ in xxxx months then you need the license). The way that you sell them also could be a factor, selling things on king snake vs selling from your own shop/website for example

Chances are if you are selling a few snakes from a few clutches a license won't be required (but check with your state and local governments. Business license are usually pretty easy to get, but can take time. There are advantages and disadvantages of them, it will require a good amount of research on the offerings local to you. (hopefully somebody from your area can chime in)