A special thank you to some great "Rockford Files" fans who solved this mystery for me! Jim Suva, Leslie Mccabe, Luis Max Delgado, Stephen P Hallberg, Bill Anderson and Henrik Hoflund Pedersen.
The below apartment building is actually on the back lot of Universal Studios
The above two images show an apartment building and the building's patio and swimming pool area from an episode of the Rockford File's titled "The Fourth Man". This same apartment building and pool area was also used in other episodes of the Rockford Files.
I couldn't figure out why I couldn't find this apartment building in Burbank or the Los Angeles area... But with the help of the above named fans... The mystery was solved! It's a fake apartment building and patio area that is located on the Universal Studios back lot.
Here's the proof..... The postcard link was found by Henrik Hoflund Pedersen and the bottom photo was found by Jim Suva. I sincerely thank all who helped!