How did you charge the previous guest who stayed with a friend @Paula677? Is your rate based on a single guest with an extra guest fee? I don't see that you have a rule about unregistered guests not allowed. The reason I bring this up is that if you change the rules after the booking, you are setting yourself up for both a negative review and possible Air BNB sanction.
I am a bit confused by your listing description and photos. Since you are new, it might be a good idea to gather feedback from friends as to how clear your listing is. You have a picture of a bedroom that you describe as the master bedroom. Is that the bedroom for the guest or is it your bedroom? Most listing for a private room show the guest only spaces and then define the other spaces a shared. Given that you are mostly away, I gather the guest has free range in the house most of the time. Then you come a few days a month the clean and I guess stay there?
