For me, as strange as it sounds given the freedoms, freelance writing is my 'day job.' I never intended to write non-fiction, but I found myself with the reality of being an adult and having to pay bills. Such is life, right?
But fiction is my passion. My partner and I decided in January that we wanted to push ourselves and get out a serialized novel for the Kindle, Nook, and iPad. We're in the editing stages of the first part right now, and securing cover art and proper formatting and all that good stuff.
One thing I will say is that you should approach self-publishing as a business all its own. You're responsible for everything from writing a tolerable manuscript to editing, formatting, finding a cover, marketing, and accounting.
Not everyone can be Amanda Hocking (who is likely slated well over the million $ mark for this coming year), JA Konrath (making $30k/month on all of his books), or Victorine Lieske (selling 10k+ copies of one book each month), but I do believe everyone who approaches it the right way can find success. There are a large number of authors on kindleboards.com selling 1k+ copies of their books a month.
If you're not quite ready to take the plunge with fiction, here's a post about an entrepreneurial spirit who's decided to publish her short non-fiction on Kindle with great results:
Katie Harper on Making Money Publishing Kindle Articles.
If you have any questions on publishing via the various e-reader platforms feel free to PM or email me. In the meantime, here are some must-reads from my blog roll, all concerning self-publishing:
E-book Endeavors by Lindsay Buroker
Written in Blood by Katie Salidas
Ramblings of an Amateur Writer by Reena Jacobs
The Inner Bean by Jennifer Hudock
Write to Publish by Robin Sullivan
And Joe's blog, a Newbie's Guide to Publishing (listed above) is worth reading all the way through the archives.
Also check out this post at the Kindle Boards > Writer's Cafe:
Kindle Primer - A Guide for Newbies and Others.
If this is a dream of yours, I hope these resources will help you on your way to realizing it. Best of luck, and if you want more resources (I have an entire section of Google Reader dedicated to these!) or are interested in a fiction critique partner, drop me a line.