OK, know I see. That is a different story. So let me ask you this. When they requested, or booked, did you inquire as to the purpose of their visit (not in a nosey way, but a "what brings you to our great area? What are some of your interests and I can help you make the most of it" kind of way?
I find that when I ask that of them in that way, they have a tendency to divulge that..."I'm coming to meet a friend who lives in the area, or I'm coming for a wedding or a family reunion"
Right there, that is a different guest than someone just wanting to come and enjoy the area or come with a partner for a proper vacation.
That tells me that someone they know, at some point, will probably be spending the night and I should let them know ahead of time, that "I look forward to hosting them and if you feel at any point you think you may have a guest, there is an extra charge for those nights and they will need to be listed. Protection for all parties".
Also remind them, after they book, that you have door cameras to verify guests, for security reasons.
I consult, Co-host, remodel and launch short term rentals for a living so please don't take offence. I just want to see people succeed in the amazing industry and help prevent some things that others or myself have gone through or had to handle. Good Luck and let us know how it turns out.