Help out a newbie?

I think the comma might be confusing the linking.  They're one to one links, so try toggling off "Allow linking to multiple records":
 

Should work fine after that:

The issue is that you have a comma in between the city and state.  Airtable will see that as 2 different records it is trying to link to.  So when you have a value of "freeholde, NJ" it is seaching for "freeholde" and "NJ" which do not exist in your base.  A fast way to resolve this is to create a new field without the comma in the deals table, remove the comma from the properties table primary key, then link the two that way.

Hi,
Yes, as @Dan_Montoya said, it's because of comma.
I struggled with it by substituting the comma with another divider, then revert changes back.
Now I have better solution - change you formula to 

Thus, your values will be quoted and when you copy-paste them to link field, they will be linked without division by comma.
Anyway, it is better to avoid, when possible, using comma (and ampersand) in the value of a primary field.

Solution with switching off 'Allow linking to multiple records" even better, but only when you have one-to-one relation. Usually a have no such relations because if records related one to one, they can be placed in a single table. 

Thank you to everyone.