I live in an area that you would think would be filled with cheap good used bikes. See, I live in a retirement area of Florida, and I thought the seniors would be selling off old bikes like crazy. It's not the case. Add to that my short stature, and there are no used bikes locally that fit me.
I did find my favorite bike on Craigslist. It was Oklahoma City Craigslist. I did a Google search for "Bridgestone XO-2" and found it. I believe I paid $400 plus shipping. I've put a few bucks into it but I'm under $800 total, I think.
It's not difficult to get a decent commuter bike for not a lot of cash. Heck, even buying brand new I'm sure I'd be happy on a $300 bike. I owned a cheap Ibex for years, rode the heck out of it, and had no problems.