I worked at a YC startup. I was employee #35-40, the company got bought out, I made about $80k from my options over 4 years, two cofounders probably made at least $50M each.
Overall, it wasn't worth it. To make life changing amount, you need to join a company where the market cap goes to $10B+, but even then a Google employee probably would make more overall and with greater reliability than most startups.