Important Questions:
1. How much did your involvement lead to the fundraising success?
2. How much did your involvement lead to the products' early success?
3. Does it make sense to take the IP early idea that you were passionate about as part of your exit package?
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Expectations:
* you should expect no cash. taking cash will lead to a lower chance of a return on your equity. if you desperately need cash, you should get a small package based on your salary.
* you have no way to protect against being diluted. you have no idea how much work it will take to make this project successful. making it successful will require dilution. at best you could negotiate never being diluted under a certain amount, and making that based on successive valuations. if you leave at pre-seed, and it becomes a unicorn, you likely don't deserve 10%. what do you think you realistically deserve if this is a massive runaway success AFTER you leave.
* one way to think about this, is what would your time have been worth at a company with a higher TC. if you would have been paid $500k including equity somewhere else, maybe you should get the same amount of equity as someone investing 500k in cash, and get the exact same dilution as they would.
* you will not find a standard answer anywhere. you need to find the best solution between:
1. your ego
2. your cofounders ego
3. giving this startup the best chance of success so that all of this time will be worth something for everyone. even if thats less than you want it to be, its better than $0. because all of the hard work lies ahead.
Small nit - protection against dilution - that may not be true; there are laws in the west coast about minority investor treatment. Your overall point -- do what you can to stay a little long and make sure the company is worth something -- is absolutely the right way to think about it.