It's highly unlikely that you'll get someone willing to work for free, unless:
a) they're trying to build a portfolio and are looking for experience, or
b) they're looking to specifically get a link on your website, or
c) they're trying to break into a specific niche, or
d) you have compromising polaroids of them.
Free text-based articles can be found in the mainstream article directories, e.g. ezinearticles, goarticles, articlesbase, etc, and you can publish/reprint from these for free provided you follow the rules regarding links and bios. The drawback here is that it won't give you unique content, which really, you need.