How could I be sure you would not default on the loan

Do you have any reputation anywhere? I may be able to send this level of
BTC to you if you can convince me of your legitimacy.
I know that he's legitiment because I bought a gift card off of him earlier today. In fact, I paid upfront and he could have easily taken my money and ran, but he didn't. Trustworthy dude IMO.
Then give the loan. Problem solved!