Why? That's exactly what a playboy billionaire should ask his sexual partners to do in year 2020 when consent can be "withdrawn" retroactively and a male is considered guilty unless proven otherwise.
Go get boned by a playboy billionaire I suppose? Why do people sign prenups? A better question is, would you, if you were a billionaire, risk having sex with someone you don't know all that well unless you can 100% incontrovertibly prove there was consent?