I have 12 yrs of corporate marketing experience and I ll be starting the marketing team handling product development, growth, brand, partnerships.
It depends highly on the company's stage - number of employees, money raised, revenue, etc.
I'd recommend you look at comparable companies by stage on www.angel.co and see what others are being offered from an equity + cash comp standpoint for Head of Marketing / CMO type roles.
This is a question that is best answered by a phone call or in person, which I'm sure by now you have secured. If not, in short, weigh the time and effort involved plus liability and risk.