I do know some professional full-time artists who live in our (rural) area.
A lot of it is clearly about self-promotion, about advertising, about getting pieces out there and seen, and about calling galleries and agencies.
These days a lot of it is about having high rankings in web searches (but don't be fooled by "black-hat" SEO companies who will take money from you, you can get good ranking without paying anyone).
For my own part I work in Web standardisation, at W3C
, and if it doesn't entirely pay the bills, it comes close. We try and make up the rest by having ads on my Web pages.
My husband is an artist, but not yet earning a significant income; he might, one day, or he might not, it's impossible to say.
We went around the unbelievably huge One of a Kind show in Toronto (I think it's 8Km of booths), and saw artists whose paintings are already all sold by the end of the first day. At prices in the tens of thousands of dollars each.
So it's possible. In Canada the collectors go for strong colours and like big oil paintings best. Here in Britain they also value detailed work and engravings, so it varies.
See if there is an art appraiser near you and ask if you can chat over lunch about what sort of piece can sell; they seem to be the best people to ask. The down side is doing commercial art, and the up side is that after you're established, you can do more of what you want to do rather than what people buy.
Hope this helps.