I really doubt that he actually has any money to spend on this, I mean he came to this forum immediately asking for a 0.01 BTC loan & promoting ponzi schemes.
I've bought some P2P exchange scripts in the past but they're heavily outdated. (they were already when i bought them.), and the code in general wasn't really useable.
( https://exchangesoftware.info/item/1-bitexchanger ) You can buy it just to see how certain things are implemented, but i wouldn't run any site with this script for a multitude of reasons. (Actually, i wouldn't buy it either.)
Really, you should make your own from scratch in most case, which can be very pricey if you want it done right. you'll either need to give someone a good equity share or probably over five figures for such a project.
If you actually were to run a successful website on that script, the person who created it really has a lot of incentive to push a malicious update. I really doubt envato checks every line of code before they let a publisher update.