Assuming you only want 1 or 2 cameras per building, what I would do is get a PoE switch for each building:
or
Choose appropriate
wired cameras for each location and install them, running the network cable back to each building's PoE switch.
Then in order to aggregate all the video feeds in one place and record them, I'd put an NVR or
Blue Iris PC at one of the locations. If you have very fast internet (100+ Mbps upload) at all the buildings, then you could do a VPN between locations and just feed the video over the internet using this VPN. But you probably don't have that, which is where the Ubiquiti radios come in. Two Ubiquiti radios with direct line of sight to each other creates a very stable and reasonably fast network link, almost like having a network cable stretched out through the air. Fiber optics would be better, but a radio link like this is a whole lot easier and cheaper.
One possible radio network design is to have a tower with line of sight to all locations, and link all the buildings to one radio on that tower, almost like you were running a miniature wireless internet service provider. That "tower" could just be a pole on the roof of one of the buildings with an
omnidirectional antenna and a
Rocket 5 AC Lite for the radio. Nanostation Loco5AC for each of the other buildings.
PoE pass-through is possible using
the latest NanoStation NS-5AC (full-size model, not the smaller "Loco5AC" version) which supports standard 802.3af PoE and has a pass-through port where you can attach a camera directly to it. If using this, it is important to use a standard PoE injector or switch to power the radio, because the pass-through port will have the same voltage as the power source. The 24 volt non-standard injector that Ubiquiti typically includes in the box won't provide power that is compatible with a camera. Myself personally, I would rather just run a separate cable and not mess around with the pass-through port which may not still be a feature when the time comes for a hardware upgrade.
Anyway one Loco5AC (without pass-through port) is about $50 USD:
Amazon.com: Ubiquiti NanoStation 5AC Loco, 5 GHz airMAX ac CPE with Dedicated Wi-Fi Management (Loco5AC-US): Computers & Accessories Plus these cheap models don't support standard PoE and they don't come with a power source at all so you need a 24v Ubiquiti PoE injector to power each one for around $12.70.
