There are 2 situations here: If the hotel charges the same rate for single occupancy and double occupancy rooms then you can book the double occupancy room and the visitor will not be charged any amount as the guest has already paid for the same. However, if the hotel charges different rates for single occupancy and double occupancy rooms then the guest on bringing the visitor along with him/her, needs to pay the respective amount being charged for a particular slot booked in double occupancy room. Also, If the visitor happens to be female and the guest already booked through the hotel is male or vice versa then some hotels may demand Local IDs or other verification in accordance with the hotel policies mentioned in the hotel policy section of hotel profile page in MiStay website.