Texas - living in an RV

Asking for a friend of mine. He asks me in an e-mail, "Where in Texas can I live for a few months in my fully equipped RV without having to pay anyone rent or utilities? I will make trips down to some town to buy water, but that's all. To poop, I will dig a hole in the ground."

I told him that I know of a cellular site where I can ask questions like these and we have at least one expert who already has an RV-type vehicle of her own. Any suggestions?

There are lots of resources but one of the first places I usually check is freecampsites.net

Here's an area I really like, for free camping: