I don't have experience of this, but it's worth mentioning that it would put you in a very different legal position then when you were working as an escort. If you're involved with running the agency or arranging bookings, you'll be "controlling prostitution for gain", which is illegal. Before you decide, think about whether your local police are the type to raid an agency, and whether this guy is likely to do dodgy stuff that would get their attention. Also bear in mind that even if there generally aren't problems, you're still doing something which could theoretically get you in prison.