There's a new plugin in the Jomres Plugin Manager called Booking Distancing.

The feature allows the system to create a black booking after an initial booking is taken (if possible). This effectively takes the property or room out of service for however many days you have configured, giving you the opportunity to give the room or property a deep clean. 

This plugin, when installed, adds a new configuration tab to Property Configuration. This tab has two options. The first enables the feature, the second for setting the number of days.