Coaching Stake

[cwar]

I had a student propose me taking a % of his winnings as opposed to charging my normal hourly rate. I recently raised my rates to $200/hour and he couldnt afford the new rates, I have a very good relationship with this student, trust isnt an issue and he has a very high paying job outside of poker but his goal is eventually to drop the job and play professionally. He is a proven winner at the 55 and 110 hu sng over 9 months ($30k profit in these) with about $80k in career winnings. He wants me to coach him while he progresses through the 220s and higher.

We came up with some preliminary terms and want to see if they are fair (we are both very new to these kind of deals), neither of us is trying to screw the other and we want something mutually satisfying:

-There will be some length of trial period
-Student plays 20 hours per week (he has a job too) at no lower than the 110s (Approximately 80-100 SNGs per week).
-I coach 3 hours per week (probably more but only 3 required) and talk on AIM or take calls whenever required
-At 80 sng per week at 10% ROI at the 110s and 5% at the 220s he would be making around $1000-$1500 per week
-I get 30% of his winnings until I have $15,000 or 9 months have passed
-If student starts playing less volume I coach proportionally less
-If I need a vacation I get to take it, I assume it will be covered by the extra coaching I give on top of the 3 hours, if its not I will make up the coaching in the coming weeks
-Students bankroll will be considered as 18k if he has over 50 buyins for the next level and I feel he should move up but he doesnt want to at least start moving up, I am allowed to reduce my coaching time until my hourly rate should equal $300/hour at his current level and winrate, students winnings will be added to his overall roll regardless of whether they are online or offline
-I can end the stake at any time

So is this fair, what are you thoughts on the terms and conditions?