Strictly, the verb let has a transitive usage. As the Oxford online dictionary confirms (and, I am certain, the Cambridge also), the verb ‘to let’ is used in its sense of allow includes the transitive sense of to rent out property (apartments, office space, and so on).
British with object. Allow someone to have the use of (a room or property) in return for regular payments. ‘she let the flat to a tenant’. ‘they've let out their house’
By implication, we can have sentences like:
The apartment has already been let
or on a notice board the one word
indicating that the relevant property has just been let
But in fact, as the Oxford Dictionary goes on to point out, there are many well-known uses of ‘let’ in the sense of ‘allow’.
“I was badly let down by you.”
“Have my trousers been let out yet?”
“He was let down from the roof on a rope.”
“I’m letting you off the punishment this once, but you won’t be let off again.”
.... and so on.