I started with three other guys on day 1 of a startup. They had money to put into the startup from a previous venture. I didn't but took 50% pay cut to lengthen the runway, as it were. After 9 months the company was almost out of money. I worked for free for 3 months after which we got the product off the ground. (They paid themselves during this time from the little money the company had left.) Two years later we had a very successful exit. For the fact that I worked at 50% paycut and worked for free, I demanded equity. Had I taken an IOU I would have missed out on a significant payday. The money which I didn't take from the company was just as important as they money they put in: without either one we would never have had time to release the product.