I need a service that can provide me with ownership of apartment
projects in the San Antonio, TX area.

One of the nation's top realtors' websites is www.livinginsa.com (No,
I'm not associated with them at'all... I simply know of their
reputation.) They can most likely help you in your search. OR - If
you're seeking a listing of apartment owners in a certain area
(multi-family) and are familiar with TX laws and feel comfortable
representing yourself in a purchase, if that's your reason for the
information - I simply call my title company here in Portland, Oregon
and they're absolutely wonderful about sending me the info. via email.
I'm not sure about Texas, but I'd suspect that if you give them your
escrow business (reciprocating for the labels) when and if you
purchase - they'd be happy to help you.