It can get complicated...
First you need to determine what areas you want to see - no single camera can capture the entire outer perimeter of a house. I bought one WiFi camera to experiment with to understand its limitations and what it would see, given its resolution and field of view.
You'll need to work out a way to run power to the camera(s) (unless you go with battery/solar powered units - fairly expensive. Cameras take enough power that batteries may not cut it.) If you find you have to run a power cable from inside it may be worth buying a PoE (Power over Ethernet) camera rather than WiFi - but you'll also need a PoE adapter or a router whose Ethernet sockets are explicitly labeled as supporting PoE.
My second camera was PoE because the WiFi signal at the location I wanted to put the camera was very weak (I walked the first WiFi camera to the desired location and checked the signal and video stream on my iPad.) The two cameras after that were WiFi of the same model as the first because power delivery wouldn't be a problem and WiFi was passable (and it was a known quantity,) but an Ethernet cable would be a tough run, even though I thought the adjustable mount on that model kind of sucked (i.e. alan screws used to secure a desired angle and the WiFi antennas got in each others way in certain directions that I just happened to want to use.)
You can find reviews of cameras on Amazon and several other retail sites, some of which specialize in such things.
You'll also need either a commercial NVR (Network Video Recorder) or a sufficiently powerful PC with appropriate software, such as "ZoneMinder", "iSpy", "Blue Iris", etc. There are a lot of choices (
https://www.unifore.net/ip-video-su...video-management-software-for-ip-cameras.html)
Oh yeah - motion detection is a feature that is really nice, since it can limit the recording of only interesting things happening, which makes reviewing long time periods go quickly. But the wind blowing through trees (whether the leaves flutter or their shadows on the ground do,) bugs flying through the IR field at night, and the ever-present spiders that insist on threading a web through the camera's night IR field of view (curse those tiny arachnid devils!) all make for more motion detection than I expected.