More often than not I've booked the girl ahead... so I know the basic cost of the session is paid for, I respect that as a risk I've taken. I'll ask the girl about her extras, then decide if I'll pay that part - I almost always do though.... I'll always have at least $150 ready for extras (generally GFE), with a reserve extra extra of 100+ in case she is a real gem and the little brain grabs the wallet!