I am a programmer not good enough with business. I am doing a project for one of my clients. It's a new software product he wants to introduce; he's so confident that he wants me to be CTO of the company/product he is going to launch and hold shares in it. I am just a freelancer. I've no problem being future CTO of soon to appear company. I am confused how and what should I negotiate with him? How many % of share should I claim as CTO as I'll be supporting all techie stuff including software and IT infrastructure. Or should I just claim my charges as a freelance project? 

This is not a technical question so I asked here...