Looks to me the entire deals favors the investors. They have 75% ownership (and hence full control) of a risky startup, which sort of failed in the first run -

Looks to me the entire deals favors the investors. They have 75% ownership (and hence full control) of a risky startup, which sort of failed in the first run - failed to take off, and people left. Now there is one committed CEO, and you are a new guy. Both key people to the success, but with only 25% stake. CEO may have some other things at stake like relationships, and his reputation etc. But you have no such thing. So decide carefully. You may have a strong bargaining position. But I don't see any value in bargaining hard for the unknown (i.e future value of a Startup). Finally, you should take a decision on how much you yourself believe in this Startup. Also the trust other people CEO and the board inspire in you. Not an easy decision.