Use CATX() if you want to insert delimiters between strings.
combined= catx(' ',catx(', ',Owner_City, Owner_State), Owner_Zip);
The problem with CATS() is the S which means STRIP(), so it throws away the space. The CATX() function will also strip the values, but not the delimiter sting. So you can create:
New York, NY 10001
from 'New York[,'NY', and '10061'
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