With regards to the DVR referred to, in my post, it too can be hooked up to the Network, as well as have an external hard-drive located 'somewhere else'. A lot of it though, comes down to where you locate the DVR to begin with. It can be placed anywhere you want it to be.
The ability to watch the 'home video cameras' on a smartphone is another thing that these units do. And hooking up to the innerwebz also allows one to save to a 'cloud', if so inclined. One of the main points though, to going with a 'used professional system' is you can add pretty much anything you want for cameras. This is opposed to "only adding another camera of the same style/quality/ability" from the same supplier. Maybe things down there in the South are different, but particular company 'packages' aren't exactly "versatile" up here.
Indoor cameras are one thing, but outdoor cameras with a temperature swing tolerance are a whole other situation. Another thing to consider.
2 Tb hard-drive with motion-activated/control settings stores a whole whack of video.