Be careful when you buying articles or other content from someone on the Internet. If 1000 of people have bought the same thing the Google or any of the other search English might punish you instead of giving you hits. To many sites having the same connect will only lead to problem especially when it comes to the Google search. So before you buy something make sure you know how many the person sold and to who and to be extra sure do a quick search for it and see if its already out there.
The best free way to do it use Copyscape.com they will find if the article is a copy or not in a second. Google new PageRank for 2008 has punished some blogs using already bought and finished articles they people buy in bulk