I think criteria to sort them out would include:
1. Whether a person has a business license, vendor license, or other documentation as may be required for a business, by the country, state or district
2. Whether he maintains a bricks-and-mortar store, or a website, for the purpose of selling figures
There may be more that we could think of (which is why I wrote "would include", and not "consist of"), but those are two that come to mind, that would tend to sort out true commercial ventures from guys who sell extras through Internet contacts like this forum, or occasionally take a table at a show, or at a flea market some place.
For me, I'm a collector, but I have traded some of my figures with other guys who had things I wanted. I haven't tried selling anything yet, but when I see some of the things up for auction on eBay, I think that I probably should. The money could go towards more figures, molds, metal, paints, etc.
Prost!
Brad