I'm wondering if saying "full-time musician" might be a more realistic term than "professional musician"? To my mind, a professional is one who gets paid, whether or not that pay is their only source of income. Also, I have seen many full-time musicians that don't, to me, meet the basics of professional demeanor and behavior. And there are lots of "semi-pros" and amateurs who always act in a very professional manner.

If your folk music is community music-making or jams with your friends, none of this applies. Folk music for pay is very different in its requirements than folk music for fun.