It is close to physically impossible before series A at the majority of startups (exception for ones which achieve significant profitability early, but that's fairly rare in the Valley) and "it depends" after Series A. As always, sought after people whose skills provably make money and who negotiate better get better outcomes. (A little bird tells me than in certain disciplines mostly related to technical marketing proven people are getting contracting rates in the $X0,000 per month region. This strikes me as highly credible given what I know about those markets.)

Equity works in reverse: the more mature the company, the less you get. Ask the YC crowd for good numbers on that.