What asset type would security cameras on a rental property be? Over how many years depreciated?

A security system is a fixed asset. The length of depreciation of the camera depends on the quality of the camera and the conditions it will be exposed to. Your vendor might give you some insight into that, but 5-10 years would be a reasonable estimate. 

Use 7 years  for  assets not otherwise categorized or 5 years if it is like a computer system.