Best quality/most accessible area for well water in Texas?

For the time being, I'm about done stacking and loading up on food/weapons, so am now shifting my focus to the search for an area to perhaps purchase some acreage for recreation/camping/bugging out. I'm in Austin, so I'm pretty central to just about anywhere in Texas. Requirement is that I can drill a well and extract decent water (which will be run through my Berkey as well). Any suggestions?

Also, generally, if you are in an area suitable for a well, what is the approximate cost to have a well dug that would supply water to a mobile home/airstream type trailer? Gracias amigos!