Have you ever worked in security? If not, I believe that would be my first step. If I were going to open a restaurant, I'd go to work in one. I think you can get a log of the basic down by learning from folks that already do it. It's also pretty low risk, though also likely low pay.
I suppose there is also low and higher risk security. The guards where I work don't carry guns or even sticks. They are just visible deterrents and wander around. That would seem pretty low risk too, but I'm guessing also low pay.