I've done a couple and they were fairly straightforward. Standalone are easy, but linking into a network is trickier.
If you use the same brand then the app sorts it out for you. I hate the idea of being dependent on an app for anything, but that's the way nowadays.
I bought the same make cameras for my home here and my Spanish place...the app just saw both and lets me switch between them as I want. Clearly this is not a commercial thing, just a domestic fun thing. The camera at home is mounted internally and on WiFi, the Spanish one is also on WiFi so all I needed was a power supply...I ran it in trunking which is big enough to take a CAT5 if needed, but luckily the WiFi is strong enough.