With the following instructions you can implement a 3-level hierarchy in the Property object in a few steps. (Your Propertybase ORG must have been setup after 2-1-2013, if older please write to firstname.lastname@example.org)
You will have to change the following attributes in the different page layouts/record types within the Property Record:
1. 3 Page Layouts (Property(The Unit), Building, and Project). 3 Record types mapping directly to the corresponding page layout (Property, Building, and Project)
2. On the Project Page Layout you will have related lists showing 1. Buildings in this Project, 2. Units in this Project, 3. Listings for this Project
3. On the Building Page Layout you will have related lists showing 1. Units in this Building, 2. Listings in this Building. You will also have a lookup field to the "Parent Project" in this Layout.
4. On the Property Page Layout you will have related lists showing 1. Listings for this Property. You will also have lookup fields to the "Project" and "Building" in this Layout.
5. You will have added lookup fields in the listing record for "Project", "Building", and "Property".