A smart home is not only for people who own the place. Everything below can be done without touching anything that belongs to the landlord, and packed up on the way out.
Lighting: bulbs and a stick-on switch
In a house you own we would change the switches. Renting flips that. Use smart bulbs together with a wireless button, and stick the button to the wall beside the existing switch with removable adhesive. You get close to the same result and touch none of the wiring.
The catch is that housemates must stop using the original switch. In practice a small label solves it.
Outlets: smart plugs, not smart circuits
Lamps, fans, humidifiers and holiday lights all get control and scheduling through a smart plug. It is the easiest thing on this list and the easiest to take with you.
Locks: ask, because most landlords say yes
Many models replace only the interior thumb turn, leaving the exterior cylinder and keys exactly as they were. That means the landlord’s key still works and the original goes back in ten minutes. Put that way, permission is usually granted.
Cameras: indoor units and a doorbell
Indoor cameras need no installation at all. For a doorbell, pick a battery model that mounts with adhesive or reuses existing screw holes, so you are not drilling anything new.
Photograph everything first
Before you change anything, take pictures. Putting it back exactly as it was at move-out saves a lot of pointless argument.
Networking
If coverage is bad, a portable mesh system is worth the money — it moves with you to the next place. It is probably the one item on this list worth buying properly.
