@Nikki133 You don't need a back-up policy. Every host determines the number of guests they accept, as well as their own house rules. It is up to you to enforce your rules. Message back to the guests stating that your listing clearly states that you accept a maximum of 5, thank them for their interest, and wish them luck in finding an accomodation that suits their needs. If it's an Inquiry, you don't need to pre-approve or decline, just send the message well within the 24 hour response time.