Go read up on the order that money is paid out to shareholders when the selling/IPO price isn't much greater than the total investment to date. The short version is that usually preferred shareholders (the investors) get paid first and will get at least their investment back and then what's left is split among the common shareholders. Also note that if the preferred shareholders are "participating" or not matters, as they may get to be common shareholders as well as preferred, meaning normal common shareholders get even less in these kinds of situations.

If your startup isn't wildly successful and you're not a founder or investor, don't expect to have a life-changing payday. The odds are against it.