It’s going to be nigh on impossible for someone to advise you without having some idea of the scope of the operation you have in mind (professionally?) and the laws in your area.
Your best bet is probably to find someone in your area that is selling something similar to what you have in mind on about the same scale you have in mind, and pick their brain.
It can be informal. If you’re thinking about selling at farmer’s markets, for example, vist the markets in your area and ask the other food vendors simple questions. “That’s delicious! How did you ever get started selling them!?” A little footwork and a little flattery will get you there more quickly than we can, here.
Good luck!