Ken,
Here is a link to the Texas State Park System for Camp Host information. We go to several Texas State Parks and always go visit with the hosts. We have never been hosts ourselves because we dont full-time RV yet (not retired yet). Many hosts travel from park to park being a host at each park for a few weeks. One way to get your foot in the door is have a current host that you have become friends with, recommend you to the park supervisor. Texas parks do like couples to be hosts. In many Texas state parks the "host site" is the only RV site with full hookups and some have telephone.
http://www.tpwd.state.tx.us/spdest/park_host/