Just looking at the contact details in the terms for that part-time jobs site, he can?t even remember his name by the end of the paragraph.
Secondly, as you say they wont put anything in writing, so what happens if you do ignore everybody here and pay, your shafted, as you can?t prove anything was ever said.
Just reading of other scam organisations that operate in EXACTLY the same way, why do you feel this could be any different?
And to finish my annual post Why not suggest if this client really wants you, they take your fee out of the commission, and see how many excuses they give you why they cant, ill bet they have at least 5.