In order to be in the 90% resident pool, you have to own property - or have a real job - according to TMDSAS:
http://www.utsystem.edu/tmdsas/medical/residency.html
1. Live in Texas for 12 consecutive months by the application deadline, October 1; and
2. Establish and maintain domicile for 12 consecutive months prior to the application deadline, October 1, by doing one of the following:
* Be gainfully employed in Texas (Student jobs do not qualify as gainful employment)
* Own residential real property in Texas
* Own and manage a business in Texas which is regularly operated without intention of liquidation for the foreseeable future
* Be married for one year to a person who has established and maintained domicile in Texas
The other regulation clarifies this further by saying going to school is not enough:
http://info.sos.state.tx.us/pls/pub/readtac$ext.TacPage?sl=R&app=9&p_dir=&p_rloc=&p_tloc=&p_ploc=&pg=1&p_tac=&ti=19&pt=1&ch=21&rl=25
(f) An individual whose initial purpose for moving to Texas is to attend an institution of higher education as a full-time student will be presumed not to have the required intent to make Texas his or her domicile;