I can fill this loan in it's entirety for you. What collateral are you offering?
Please re-read.
So in other words you cannot offer anything to guarantee that the lender is going to be repaid in full?
Apparently so, except for some proof that he's been getting some transactions via PayPal the past couple of years. Really, there's nothing that forces him to pay the profits to the loaner so he could very, very easily just continue with the website after you paid him $15,000 (even if he has a good intent right now). I'm not really sure why transactions via PayPal is supposed to prove that you are a trustworthy guy that will repay the invested amount, either.
If proof of my income through PayPal reports isn't enough to prove I can turn a profit then this won't work for you. I also have reputation on forums, business history, etc.
Tough luck, then, because it's not going to be enough for anyone around here.