Lets calculate. Assuming u work for $70k/year usually .. the expected payout shud be $3.5m after 1 year for the offer to be reasonable. This is an expected payout .. assuming a 33% chances of success given that its a "good" idea .. the company shud be worth at least $10.5m a year later. Given that u are taking such a risk .. and will do lots of the work .. u want 3-5 times that money at the very least .. so do u think the company might be worth $50m one year down the road with a proability of 33%?

Hmm .. the calculation is really slightly orthogonal to ur question perhaps