Get a pfSense / OPNSense box, it doesn’t have to be expensive, I use an off-the-shelf AsRock J3455M motherboard with 4 gb of ram and a 4x Gigabit Ethernet PCI-E expansion card (completely overkill). Due to lack of budget, I’m also testing an Intel NUC with a USB 3.0 Gigabit Ethernet adapter (would not recommend the later though).
You only need 2 ports, 1 for WAN, 1 for LAN. You can also get away with 1 port if you don’t do a lot of traffic between LANs and you have a managed switch, which is basically a must if you will have any IoT devices, like security cameras.
My personal recommendation would be any Celeron / AMD equivalent (usually AMD embedded something) small box with 2 Gigabit Ethernet ports, like a MintBox Mini 2, 2 or 3 Ubiquiti AC Pro APs, any 24 port POE switch from Ubiquiti (POE for the cameras and APs) and add to that whatever other switches you need (just don’t be overkill with the switches near your end devices, too many and you could bottleneck the single Ethernet port coming from the main switch). If you are able to, you should rather do some patch panels and separate cable runs, rather than remote switches, but that’s just my opinion.
For the cameras, I’m completely out of the field. Wendell did some interesting hackaroos voodoo doodads to get very cheap “bricked” HIKVision cameras from eBay to work (it’s not that hard). Unbricking Hikvision IP Cameras (Repair, Reflash and TFTP Guide)