I wish lmao. I don't have the skill nor the time tho :c I have done some comissions and designed some stuff but yeah, I'm not a pro by any means.
Answering your question, I guess to be consideres a professional artist art should be... Well, your profession x'D The thing you dedicate most of your time to and that pays your bills. There are exceptions obviously (for example a dude whose work I love is a college professor, but he has published comics and they're quite, quite famous here in Spain. I consider him a professional artist even tho his main income isn't art. It's hard to trace the line).
There's also the skill gap. For example, I'm able to translate a text from English to Spanish with ease, but I'll not do it nearly as well as a professional translator, since they have studied how to do so correctly for years. Same with art, I could draw a comission for someone but my skills are not the ones of a professional.
I hope that made any sense. As I said, it's hard to draw the line, but those are the factors I'd take into account when separating them.