I can tell you here in NJ you need:
1) To form a business with the state, get federal and state tax id number, as well as sales tax resale certificate
2) Obtain business insurance
3) Register with the health dept.
4) Obtain the use of a health dept. inspected kitchen
5) Register with the local municipality (fire requirements, etc)
I'm sure I'm missing something else, but that's the big stuff. However, if you get into the right sales opportunity all those hoops you gotta jump through are worth it....