They’re affordable and ubiquitous, but homeowners shouldn’t be able to act as vigilantes.
Look up the brand Intelbras they have a few residential intercoms that might work for you, I don’t know where you are , but i know they exist the US and some parts of Europe and they might be cheaper there since they’re a brazillian company (they’re the best one we have I think?)
I have their regular câmeras and they fit all our criteria. Ours are online, buy ots by choice it’s not a system requirement. At least a few years back a few of those intercoms with screens were compatible with the nvrs i believe.