Hi @Brady---Shae0 - I can understand why you would be unhappy about this. It sounds like someone plans to use your space to run a business event.
Don't dismiss it out of hand, I'd say give it some consideration. If they plan to have a low key retreat, with no parties or risk to your property, then it could work very well for you!
Some hotel owners encourage business event bookings, so it depends whether you want this kind of business (as it often turns into repeat business if their event is successful). Sometimes regular hotelliers (with larger spaces) would use the event as an opportunity to offer extra's and generate extra income streams during the event - not to mention all the extra advertising! These often benefit both the organiser and yourself as the host (i.e. you could offer to hire a licenced external caterer and split the food profits) so you might want to consider discussing it openly with the guest who has booked and understand what additional risks or opportunities the event brings. Weigh these up and keep an open mind, as it could be a lucrative repeat business opportunity.
That said, if they booked your entire property (all 12 rooms) and plan to resell it, then you should check to ensure it's not against Airbnb rules. There are rules about reselling bookings, so you'll need to ensure you maintain control of who comes and goes. If you don't get to approve each attendee at the event, then I would say it is too high risk - as your home insurance and Airbnb host protection will likely not cover you for damage.
