My wife was driving through central Florida when she got to see something that surprised her, even though she's now lived in Florida for a couple of years: a roadside knife stand. I have to admit, I was even a little taken aback. My first question for her was whether or not she took a photo of the stand, which she did not. I'd seen oranges and other edibles before. Nuts, watermelons, etc. Shrimp, even. And you'll see people set up yard sales right out to the street, maybe with antiques (or just old junk). There was a place along Locust in Milwaukee where you could pick up a used appliance right from the sidewalk, which was a little odd, but you can apparently get cutlery along a state highway in Florida.
My understanding is that anyone who sets up on public property along the road would need some kind of a permit to sell. Even the homeless in Jacksonville are supposed to have a permit to ask for money. I will assume that this guy had said permit from the local jurisdiction. If he didn't, I would not think that a knife stand would last very long along a state highway. Unless, of course, he was the off-duty local sheriff.
If this man had been selling fruit instead of blades, he would have fallen under the Florida Cottage Food Law, which allows him to sell with:
no license, inspection, or training from the ag department.
That's good for up to $50,000 in Florida, and I am sure if you can make a little more than that in cash, no one's going to notice.
I found some information about roadside fireworks stands and roadside flower stands in Florida, but knife stands were not really addressed. Probably because no one ever thought someone would sell knives along a highway in our state. However, I think that just about anything will be attempted at some point in Florida, so there probably does need to be some kind of regulation as to what can and cannot be sold along the roads. Like guns, exotic animals, and probably fireworks (which are basically illegal to shoot off anywhere in Florida).
The best bet is to resist your temptation to stop and check out the inventory. When no one stops at your (hopefully) illegal roadside stand, then you don't set it up too often in the Florida sun.