Figure out your talents and how they can be expressed online, and then find the people who are paying for that. It may seem like a generic answer, but unfortunately that's as specific as it gets. There are so many things one can do to earn money legitimately that the answer is different for everyone.
For myself, I've been earning online full-time since 2007, and am the sole income-earner for a family of five. I write for clients I found primarily on Elance and through referrals, and in custom writing groups. I also took a lot of general transcription work when I first started. These open-submission sites are a way to build up recurring revenue, but they're a LONG way from paying many bills. I also design and sell beaded micro-macrame jewelry and extra bead supplies, mostly through Facebook groups and Etsy.
So -- yeah, there's a way to make a living online. It will take time, patience and creativity, and probably a lot of self-education.