Factors to consider: (or, why nobody here can give you an answer) 1. How much do you need? 2. How much of a cut do you want? 3. What is their established sal

Factors to consider: (or, why nobody here can give you an answer) 1. How much do you need? 2. How much of a cut do you want? 3. What is their established sales volume? (You can lower the percentage if sales volumes are high.) 4. If none, what's their expected sales volume? 5. What's their expected sales growth rate? 6. What is your estimate of their numbers being accurate? (i.e. Cut their expectations by 30% and see if it still works for you.) 7. How much time (in actual $ per your hourly rate) are you expecting to put in on this project? 8. How much time x 30% are you expected to put in? 9. How much is that IP worth to you? 10. How much is it worth to them? 11. How much is it worth to others? Answer those questions, and then it's just a matter of relative comfort. There's no set formula here, your cut is as big as you want, and as big as they want it to be. IMO, set properly, Option C is the best for you, because eventually, you'll have income for no work. That's the reward for the risk you're taking in not being compensated up front. Make sure that reward exists.