First, check your local and/or state regulations to see if you need to be licensed specifically for security, yes even just to prewire. In my state, installers require state license, background check, and testing and companies require at least one company agent that is essentially an installer license but with X amount of hours working in a managerial position in a security company.

Second, check your liability insurance as most require a larger premium and possibly a dedicated policy to cover security installations.

Third, is you saving your contractor a phone call worth you learning on the job? I'm not saying don't do security, but learn it on your time and your own system where you can really pick it apart and master the system before you install it for a client. It's not super complicated but each system wires and programs slightly different.

That being said, if you are determined to do it, here is a few off the top of my head. We run 22/4 for pretty much everything except smokes that require fire rated wire.

keypads
Sirens
Doors
Overhead doors
Windows
Motion detectors
Glassbreak detectors
Water sensors
Freeze sensors
CO detectors-please check your local codes for these
Smoke detectors-please check your local codes for these