@Chris16026 If by "established" you mean that it will have a history of reviews, what Helen was saying is that you have to "start over" because the ratings and reviews and any future confirmed reservations are not transferrable.
You have to start a new listing with no reviews and no bookings regardless of whether you buy a house that is currently being used for Airbnb, or just any house. The only advantage in buying a place already being used for that purpose is that it might come furnished with all you would need.
If the seller tells you they can just transfer everything over, they would be wrong.