-
Switches are pretty cheap. Keep an eye on Amazon on the Black Friday deals, there are a variety on there. I got this for £13 the other day https://www.amazon.co.uk/dp/B007DHTX7Y/
Will be a bit more expensive with PoE, although you can always use the separate PoE power adapter that come with the access points (it plugs into the mains and you plug the network cable in and then another coming out with power so still only one cable going to the access point).
One point, that EdgeMax router can act as a switch too.
You can either have all ports on the same network (like a bog standard home router), 2 ports on one network and the rest on another (this is what I use) or each different port a different network.