@Gary8
You want to distinguish between the two things:
A booking inquiry
A guest is asking you something about your listing before he makes up his mind and POSSIBLY firmly reserve your listing. If you feel that he may be a good guest, you are perfectly fine with pre-approving his booking. Remember that this pre-approval is only conditionally binding. Yet another potential guest may be inquiring with you for the same time frame and the same listing. You are perfectly fine to pre-approve him, too.
A Reservation Request
In the meantime, yet another guest requests to book your listing in the same time frame. You are perfectly fine with accepting this reservation request. The Airbnb will automatically lift ALL of your previous pre-approvals and accept the firm reservation on the spot with no penalty for you.
In other words, Airbnb is keen on facilitating firm, paid for reservations. This is where both their and your income comes from. Inquiry pre-approvals are ways of allowing the guests to really shop around, and decide whose pre-approval will they (or not) convert into a firm, paid for reservation.
My experience shows that guests who go on asking many, many questions only to decide to book at some later point in time, usually do not get to book the listing they really like because someone else snatched it away right before their noses.
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