Staking a friend

[Kips Bay Kid]

What are fair terms for both parties in terms of %'s.

Consider these two different options:

Option 1 where the player takes on no risk, meaning if I give him X dollars and he loses the full X dollars he is not responsible for paying back any of it. What percentage of profit should I allow him to keep?

Option 2 where the player is liable for losses he incurs. What percentage of losses should the player be responsible for repaying and what percentage of profits should the player be allowed to keep in profit?

If there are any good articles or discussions that have already taken place on this subject I would be happy to read them.