Get the equity in writing and witnessed by a lawyer. you are in the place I was 10 years ago. I have been well shafted by my "mate" (sales and marketing)who now seems to think that he owns the company we started together. Though this guy was a lot more experienced than me his marketing ideas were rubbish and old fashioned. I have had to design all the products and also fight his out dated marketing methods as well. What matters to these guys is how much money you invest (the risk), they think your time is free and therefore "worthless". I now look after a team of 12, pray my invoices gat paid every month and wait for the axe. I have a tiny house and a 4 year old pickup truck. Before I met this guy I was earning £100,000 a year :(