mail address/physical address in different states

Noob question here......if you're full-timing it (as I am considering), what do you need to declare yourself a resident of state X? I'm a WV resident, and my plan has been to become (somehow) a resident of Texas due to their military retirement perks before I leave the WV Guard. Before considering RVs, I was planning on getting some land, but I noticed that one RV organization offered (as part of their paid membership) a Texas address? Is that sufficient to be a Texas resident??