Inside your flat
Cameras positioned entirely inside a private apartment are generally simpler than cameras facing shared areas. Tenants should still check their tenancy terms, avoid areas where anyone would reasonably expect privacy, and confirm any restrictions before permanent fixings are made.
This alone covers a lot of what people want. A camera inside facing the door records anyone who comes in.
The front door and the corridor
This is where it gets less obvious. You own your apartment. You do not own the corridor outside it, or the external walls of the building. Those are common property, managed by the building.
So a camera mounted in the corridor, or one drilled into the corridor-side wall, or a doorbell camera fixed to the outside of your door frame, normally needs the building management's agreement. Some buildings allow it without fuss, some allow it with conditions, and some refuse.
Why buildings care
Two reasons. The first is that a camera in a corridor films your neighbours coming and going from their own homes, which raises reasonable privacy objections. The second is fixings and finishes, since management is responsible for the condition of common areas.
Buildings that do allow it usually want the camera angled to cover your own doorway rather than the length of the corridor.
Options if the building says no
A camera inside the flat facing the door still records anyone entering. Some doorbell-type devices mount within your own door or door frame rather than the corridor wall, which can change the position. A wide-angle indoor camera positioned to see through the door when it opens covers arrivals.
We can look at your specific door and layout and tell you what is likely to work.
Tenants
If you rent, you have the same position on the inside of the flat, though it is worth checking your tenancy for anything about fixings and making good when you leave. For anything outside the flat, both the landlord and the building are relevant.
Most tenants use setups that need no permanent fixings, which avoids the issue entirely.
Balconies and windows
A camera on your own balcony covering your own balcony is normally fine. Pointing it outward so it films other apartments, their balconies or their windows is not, and will draw complaints regardless of the building's rules.
Ground-floor flats with a terrace facing a shared path are a common case. The camera should cover your own terrace, angled to keep the shared walkway out of frame as far as possible.
Getting it right first time
The owner or tenant should confirm the current building rules before installation. We can then plan positions around the approved areas and practical cable routes.