IMO, the best way to work is "don't ask, don't tell". I don't ask them anything that isn't important to book, and don't tell them anything that isn't important to the booking. If they ask if I'm single, I just say "I don't like discussing my personal life".
I will say though, I approximate that 80% of my bookings are married men, with some telling me, some having her as their WhatsApp or lock screen pic, some wear rings etc. These tend to either be the best/most respectful in bed, or efficient in-out-gone style. I have personally found that most of the single men are either unhygienic, clingy, or try to push timings or boundaries. I have lost count on how many middle aged single men have asked if I'd date them.
But like I mentioned, don't ask, don't tell and you'd likely never know. If you do find out, finish the booking and don't allow them to rebook you.