I made bank when I owned mine. Its not something you could rely your sole income on, but it is a good side line money maker. I was engraving pictures onto pendants in the mall. The mark up was outragous. Almost penny to a dollar.
I'm assuming the laws varies on different states. In florida you will have to acquire a building and let the DMV aprove of the location first. Then from there you shoul be good to go. 50K would prolly get you started.