Help finding the owner of a rental property to mail a letter?

[Paul Tibok]

I have been looking for a duplex to purchase and owner occupy for quite some time in the area I am currently renting in with no luck.  I recently drove around my neighborhood and wrote down 42 addresses of duplexes not on the market in hopes of finding the owner through property tax information.  Can someone please direct me in the best way to get in touch with the owners of these properties?  Using the county website I have not been able to actually locate anyone.  I have heard through the podcasts people finding deals this way so please any advice would be great! Thank you.