[tikna]

With this attitude, they will hardly succeed. I've been through this situation in the past.

You will be blamed for 100% of the stuff going wrong on technical side, and will be given 10%. Moreover, I don't think you will be able to keep yourself motivated with this kind of attitude within the team. You won't be a considered co-founder, just a technical guy to finish thing off. Remember "Ideas are worthless".

Don't settle for 10%, not even 20%. Its not about money, but how much they value your work. Coming up with an idea is not a big deal, but execution is.