Open source and free software aren't synonyms.
When seeking tools to help my 13-year old son learn Python this last week, I've come across many with dollar signs attached.
If you're writing tools or simple applications, how else are you to make a living?
The two primary routes to open source survival, however, are services and service. IBM makes a ton of money from open source services, integrating systems based on open source operating environments. Linus Torvalds makes his money from service, taking a salary from the OSDL.
The business model you choose depends on where you sit in the open source ecosystem and what you need.
But if you're studying open source, please be assured that a living you will have. If you want it.