In the sims 4 the ability to lock door returns in patch 21.
Lock doors in sims 3.
I have my front door locked to everyone except household and i ve hired a maid to clean my house.
At that point the door will open by itself.
While door locking settings are usually honored in some circumstances they may be completely ignored such as a burglary a repo man visit or a confiscation made by the social worker.
Unfortunately the maid just waits outside my house until i have to manually dismiss her.
Im sure if you ask arond the people who make realy good sims downloads you might find a sims 3 version of it or someone willing to give it a shot.
Now the door will be invisible until the player selects inspect at the wall and discovers the door there.
Once the player walks through the door.
The sims 2 featured a download on a unofficial site that was a 5 lock bank door were a sim with a key could lock and unlock it but people without one couldent.