We have done this type of situation. We have told them that as a short term rental we are not licensed to rent for more than 28 days at a time. But they are welcome to do multiple 28 day stays. They are taking their chances on whether I will have availability after the first visit. But usually, after the first couple of weeks I have a sense of them and I might be willing to block the upcoming calendar until they are ready to book it.
I think these scammers target new listings. I haven’t seen them on my older existing listing, either.