I've personally been quite pleased with the combination of Frigate and some Amcrest POE cameras. Just make sure the cameras you are getting support RTSP though and you should be able to use them with Frigate.
Also make sure you block the cameras from reaching the public internet using your firewall, and only make them reachable from your Frigate host. Personally I use a VLAN with no internet access and enforce tagging at the switch level (i.e. don't trust the cameras to maintain their own VLAN) settings.