Generally speaking, 50/50, 60/40 or 40/60. I personally wouldn't want to stake someone who only wanted 30% of the profits (wouldn't trust them lol) and likewise I'd be wanting at least 40% for risking my own wonga. Obviously depends how good the horse is, why they want staking etc. Id probably stake a good player with a good reason for needing staking and be prepared to take only 40%, but if say they were an up and coming player/bad BR management etc Id want 60% and would offer to help them with a bit of coaching/hand analysis etc
If you trust the player and he is good, 50/50 makes sense and takes away any possible tension made by one person getting a bigger share.
Big thing for me would be making sure you get the same split of rakeback/loyalty bonus/sign up bonus etc, because this is obviously huge at the 200nl level. Id also want them to have a good loyalty deal
I seem to recall Longy once posted a link to a 2+2 article on cash staking that was very good.
If I was staking a cash player, I'd also want to have input into where they were playing and how they game select. I would never stake a 200nl player on
Full Tilt for example, so many easier places to play.