The space requirements get super intense with many cameras like that unless you compress the video. And if you compress it then with so many you need the camera to do it on the fly otherwise your server needs to be really beefy to handle real time encoding of 10+ incoming video feeds. Also if the cameras don’t encode then the data flow would congest your network something fierce. Those requirements might push the cameras from cheap to not so cheap though (still far from expensive though imo)
The biggest issue as I see it with so many cameras would be how to find interesting stuff in all that data. If it’s only surveillance then sure you can just retain like a week of feeds and make a vacation mode where you store enough to cover the whole vacation. But if you want to look at what your dogs do etc then trying to track them across 10+ cameras is going to be tricky without some software help, unsure if there is anything open source for that.