Reolink cameras are pretty affordable, can be accessed with ONVIF, and you can just put them on a VLAN/Firewall that has no internet access if you're afraid tha

Reolink cameras are pretty affordable, can be accessed with ONVIF, and you can just put them on a VLAN/Firewall that has no internet access if you're afraid that it's phoning home. I have a Synology NAS and their free security camera software is pretty easy to set-up and use with ONVIF cameras.