If you have tried to create your own property pages within Safari Portal, you would have encountered the field "Link To Master Property Page" as seen below.
Safari Portal is simply asking you to type in the property name to see if a master version of this property already exists within the Content Library. If one does exist, it will link your new page that you are creating to the Master Property Page.
If a Master Property Page does not exist within Safari Portal, you can simply type in the name of the property and click "Enter":
Why Does My Page Need To Link To A Master Property Page?
This is for the purposes of providing analytics data at a later stage. Analytics reporting is a planned future feature that will help give agents valuable insights into their existing business.