Build tools to help automate simple things you do every day. Build tools just for yourself. That way in a couple years you'll already come to the field with a huge portfolio, and who knows one of your random projects might actually end up getting popular and making you something.
I started making personal projects at 15, worked under my mom's name for freelancing sites while <18 (illegal against their ToS but oh well) and now I'm leading a team of people at a big company since I have 9 years of experience and 5 years of experience with my specialized field (Android).
Just build something.
Simply having an open source project in itself brings in no cash. Can either of you (or someone else) go into detail on your experience? Links are OK! The OP (and myself) would love inspiration :)
Then decided to learn JS and node and started writing a web real user monitoring system based on http://github.com/bluesmoon/boomerang. While at it submitted PRs to upstream and engaged in the community mostly with complaints about sftandard stuff missing and modules not being in a good state.
Now I work in the same company as the guy who created boomerang and lpve every minute of it.