i feel like i'm answering someone's thesis for a college report.
simple answer - selling art is hard, don't depend on it if you can. if it's the only thing you do you need to either sell really well online, or supplement it with shows etc (but not everyone wants to do that, i know i won't.)
otherwise it's a hobby, even if lucrative if you have a job, don't quit it for art. to be a full time artist you need to either push your work aggressively and have the personality to do it. and also, to make new works almost constantly. you'll be working harder at this with longer hours than at a real place.
beyond that i'm not validating anything because i don't see why i have to.
---Mike Savad
MikeSavad.com