I just go to elance.com and hire people who are in the "field" of my niche that I'm working in. I put it in the ad on elance.com that they have to be US or Canadian and work or have experience in my niche. I hire about 8~10 of the people that apply for the writing assignment. So, I'm spending $100 or so to test out the writers I've found and then hire 1~2 of them to write all my content for the site and usually pay them $2.0/100 words with articles being around 700~1,000 words each. So I'm usually in a site for about $1,500~$2,000 in content.
You're wasting your time screwing around trying to get content cheap. You'll usually end up with crap content which will effect your conversion rates and increase your bounce rates.