Welcome to WildTexas.com, Zeke!
Our
Web Guide is a great place to start -- it lists
all the RV rental and sales locations that I am aware of in the State of Texas (if I've missed any, let me know!). Check it out:
Recreational Vehicles (RV) Web Guide
If nothing else, there are some good RV/trailer camping forums linked in there that would be useful to lurk on and see what folks are talking about -- good places to rent from, particular brands or models to avoid, etc.
I do highly recommend renting before making the big investment in purchasing one. I know our pop-up experience in Big Bend taught us a few things, and made us better informed if we ever invest in some form of haul-along camping/living accommodations.