The law classifies you either as a Texas resident, a non-Texas resident, or an international student. To qualify as a Texas resident we just need proof that you've lived here for at least a year immediately prior to your date of registration.
If you're not a U.S. citizen, we'll need a bit more documentation:
If you're eligible to establish domicile in the U.S. you may be eligible for classification as a Texas resident. Here are the categories set by the Immigration and Naturalization Service:
Undocumented immigrants who meet our admission requirements can enroll, but normally will be subject to the non-Texas resident tuition rate. You may qualify for the Texas resident rate if you meet all four of these qualifications: