I disagree @Sarah977 & @Gail600 !
Here in the UK we don't have air con, but we do have central heating. If I have guests during winter, autumn, late Spring, I turn off radiators in guest bedrooms EVERY day, after the guest has left in the morning, & turn it on again at an appropriate time of night. Similarly, I shut any open windows. At £20 for a single person, & £30 for a couple, I can't afford to waste fuel.
In the UK, the law allows home owners access into guest space in the owner's own house. Obviously I knock first, in case they are still there.
This subject is frequently discussed here in the CC. I have the impression that Americans have a great sense of entitlement that no one should enter 'their' room during their stay.... In the UK, I think there's more of a feeling that it's the landlady's HOME, so she can go in if need be...... But then I wouldn't be so unreasonable as to waste heating & make the house freezing in cold weather, nor waste aircon ...
The booking for one, then messaging "We'll ..." is more of a problem if you charge less for one & more for two.... When this happens to me, I ask if there are two of them & request they amend the booking to two people, for which they get charged the second person fee.