Backing question <--- noob

[hoops886]

Ok I'm a complete noob when it comes to backing. Have never had an ounce of experience on either end. Plus I don't even know if this belongs in this forum, but whatever.

Well my friend said he'd back my $500 in a live event. We also agreed that even if I didn't cash, I'd pay him back the buy in 100% eventually (like 25 bucks a week or something). If I do cash, what kind of percentage of the profits should he get seeing that he's not really risking too much?