Twelve or so wireless cameras will not work, they will over load the wireless network. Run the network load numbers
Also for a security system wireless cameras are very unreliable. It is relatively easy to jam a wireless network.
If you need to run power to the cameras you can run POE ethernet.
Please read the cliff notes and other items in the wiki. The wiki is in the blue bar at the top of the page.
Welcome to the forum from another Texan (DFW area). I started out with a couple of wireless and it didn't work very well for me, seemed like something in the neighborhood would interfere with the cameras for a couple of minutes to as much as a couple of hours (I tried different wireless channels, wireless access point). I decided since I had to run something to the camera anyway (power if wireless) I might as well use poe and have one cable supply power and a steady signal. I've never regretted getting rid of the wireless.