While that can be true for employees, founders' stock works differently than options granted to employees. When the company is started, founders write a check t

While that can be true for employees, founders' stock works differently than options granted to employees. When the company is started, founders write a check to the company for a very modest amount (~$100) and buy all of their equity up front. They can do this legally as, on day 1, the company doesn't have any real value. And because the founder has already bought her equity with the $100 check, she never has to pay anything else. If she leaves, what's vested is hers.