A friend shared this link covering the dubious financial prospects for professional writers (in Quebec, but I'd bet the prospects look about the same in the rest of Canada, and indeed in the rest of the first world). My response to her seemed to amuse others, so now I'll share it more widely:
Published authorship is a star system, and it sounds like cynical craziness, but widespread literacy means a lot of people have the basic tools to become a writer, which means supply swamps demand at the non-superstar end of the market (think of pro sports, in terms of the rewards at the top, the relative lack of depth in the middle, and the total lack of demand for mediocre athletes) except with a less-clear system for detecting and recruiting superstar talent.
All I can suggest if you really desire to write, as the distilled advice that writers usually give on how to write, and the experience of people I know who write for a living, is this:
1) probably don't do it
2) if you must, write lots
3) periodicals of all kinds are great opportunities to work up your writing chops in a paid way, as well as working on essays that might become books. It's surprising how far you can get with a few well-targeted query letters.
I think a fourth element is blogging, in that I see a lot of star bloggers who just reflexively emit books after a while, and the nice cycle there is that the blog acts as both a creator of the book's audience, a promotional tool for the book at the end, and a way to practice the craft of writing and test the ideas you are writing about. The pay is quite bad, of course, and the difficult part is the bit where you become a star blogger.