Standard 24 hours. If the contractual process is not completed within 24 hours of the approval of the reservation request (or not at all), the landlord has the right under the lease agreement (see Article 6 - Other Arrangements, paragraph 5) to cancel the entire reservation. It is only his responsibility to decide whether or not to wait for the process to be completed.
So if you already know that you are not able to complete the contractual process within the 24-hour limit but still want to finish it, please contact the landlord through the Messages section of My Housing web app to explain your situation. We believe that together you will come to a solution.