A friend staked me and we never solidified the deal beyond 50/50, can someone help me hammer out a fair deal?

Hey gang,

I'm really just getting started playing, I've been the best of our friend group in home games and I decided to start playing online. I play tiny stakes, because we're all mostly poor college students.

As kind of a joke, I asked a buddy to stake me for 50$, and he actually did. The deal was 50/50 with a renegotiation at 150$. Again, I play tiny tables- 10c/25c blinds. Over the past 3 days my bankroll is now as around $200, from my initial starting $50.

My question is whether or not cash game stakes are generally capped or uncapped? To me it seems fair that at some point, the staker would have his profits capped. My initial thought was that once(if) I made double his stake, his profits from the 50% would be capped(so he'd see a 50$ return plus his 50, and he would have the option to restake me). After some thought though, he's looking at the chance of a 100% loss or a 100% gain in that deal, with the odds changing based on how hot I run. With that in mind, a cap in a different place, at like 200% or 300% may be more favorable.

However, neither of us are serious poker players, and we don't know the ins and outs of staking deals. For those of you with experience in it, is there usually a cap for cash game staking, or will I indefinitely owe him 50%?

I don't want to screw him over or anything, I just want to make a fair deal for both of us, and I'd like some input from more knowledgeable parties. Any advice would be appreciated