My friend asked so I'll post it here as well. I'm no expert at it so I can not really give out any tips, having good drawing skills, building fanbases are the very basic, those take times and social skills to do and it's not like I have either of them anyway so I'm not talking about that here.
If you think your art is good enough, and wanting to make some quick bucks, but don't know where to start, here're some links I think maybe useful:
DA's forum jobs offer:
https://forum.deviantart.com/jobs/offers/
Lots of people don't really care about the forum so they don't know about this, so I will just put it here anyway.
Reddit #hungryartists