Thank you for your quick response. I have put your advise to good use. It has helped me perfectly.
Now I have one other question: Could you please tell me how I can ensure, that guests can only book the vacation homes during certain seasons like Christmas and NY for one month or more.
It can be set by (probably even the same) rules, setting the minimum stay to the amount of desired nights
BTW
Airbnb addresses reservations for 28 nights and more as "long term stays", automatically overruling your choosen cancellation policy by the "long term stay" cancellation policy.