Wow, great thread, so many good ideas!
Here's my two cents...
The most of the money I've made with my art were gigs I landed in sites like Upwork (the old oDesk).
There you can search for jobs that interest you (say, for instance "children's book illustration") and apply for them. Once you do a good job, people will recommend you and and raise your "grade" and you'll get invited to a bunch of stuff and so on.
Of course, there is the bad part: it is hard to get reasonably well paid. Most of the clients are interested in cheap jobs, and since they can choose, they'll be likely to choose the cheapest. Since I was living in Brazil, where the currency is weak compared to the dollar, that was ok for me then - because when converted I'd get twice the value. But you might have to accept some very poor offers at the beginning, so that you can build a name.
The other big thing, if you're a beginner, is: you will not get to draw what you want. In fact, most of the gigs I landed weren't remotely fun to start with. For instance, these drawings I've made for a rug shop:
There were, like, 16 just like this one. Were they fun to make? Nope. Am I proud of the result? Not really. Did I learn anything with them? Possibly not.
The payment was decent, though.
And this is the really nice thing about this work-for-hire experience: you learn how to behave professionally.
It's not always fun and rewarding. It's a job, like any other, but one you happen to be good at, and let's face it, no matter how boring the drawings you have to make are, they're still better than many other jobs.
At the same time, I have a comic here in Tapastic that gets me almost no money at all. But I love it so. It is so rewarding to talk to my readers and to see this story I'm telling be unfolded, a page at a time...
What I mean is that you need this part, too. You need to find your balance. I guess we are all searching for the same thing, huh?