Cost depends on depth, size of pump, tank, and the big one is electricity hook up. If you have to drop a pole and hook up a meter that could cost more than the entire well.
Figure $8 to $10 a foot to drill it and put in casing, etc. Another grand or so for the pump and cable and tank. 5K to 10K sounds about right. Most wells in Brazos Co are 250 to 350 feet deep. Robertson Co can go greater than 500 ft depending where you are located.
All well drillers are required by law to register well for human use.
Again the hidden cost can be the electrical part. Best to dig well as close as possible to existing sources of power.