In my opinion you should spend as little as possible on free site content. Hello - it's a free site! We don't want to give the surfers exclusive or even particularly unique content.
On the other hand, you also don't want to use content that's way overexposed.
There are dozens - if not hundreds - of content providers with nice sets of content, cheap, that hasn't been seen everywhere. I'd post my own list, but that would defeat the purpose.
