You’ll be able to create multiple spaces in the next version, so you’ll be able to easily re-create those examples.
You can’t “link two databases” in Anytype at the moment. See Automatic Bi-directional linking + Rollups .
There is no way to access relations of other objects either in sets / collections. You can only connect objects to other objects (through the object relation type). For instance, you can connect a building object to a tenant object, and then you’ll be able to see this relation either in the object itself or in a set / collection. But you can’t connect the building’s address relation to the tenant object atm. You would need to add the address directly to the tenant.
Adding a third object (apartments) to the mix complicates things even more.
I recommend simplifying your approach a bit if you plan on creating something like this in AT until bi-directional linking is introduced.