For a single tournament 60/40 (60 on the player's side) is terrible for the investor even for a great player. See my post at the bottom of
this thread for a complete explanation.
In the situation of being bankrolled for long-term play in cash games I recommend deciding in advance that when your bankroll increases to $X the backer receives his initial investment plus some additional amount of profit. The thing is, the extra profit the investor receives is primarily compensation for the risk of a loss - if you're a good player and properly managing your bankroll (i.e. moving down in stakes if you start of on a downswing early) there really isn't risk of loss so much as risk that it may take a long time before you've earned enough to pay them back.
If you are sure you're a winning player I'd recommend trying to get an interest bearing loan from your friend for most of your bankroll, say for 75% of it, then stake you for the other 25%. Just let him keep all of the profits on that 25% of your bankroll until you've made some preset amount of profit, at which point you give him a quarter of your current roll. The 75% loan you pay back when your roll is even bigger, or after some predetermined amount of time, and you include some preset interest rate on this portion.
So if he gives you $1000, of which $750 is a loan at a 7% interest rate and $250 is towards staking you, maybe when your roll is $2000 you give him a quarter of your roll for his stake (so you give him $500 in exchange for his $250 he provided) then after a year you pay back the loan for a little over $800 ($750 with 7% interest for a year).
This lets him get a portion of your winnings for his service, but if you're a solidly winning player he doesn't deserve a huge share as really you're just taking a loan from him rather than him participating in a risky venture.