I think there must be a reason why these tenants are willing to be a crowded apt. Do they have a history of no/ poor rent,illegal immigrants,want to be with their friends/classmates/co-workers.
Driving around Canberra, I have noticed some balconies with curtains, and wondered if there were people sleeping there.
These 12 tenants may all work different shifts, and at any given time, not too many are home.
If there were 2 sets of bunk beds in each bedroom, 2 sets in the loungeroom, one set in the dining area and possibly a couple of cots on the patio.....
Nothing wrong with renting out beds.
Years ago, when people had a dozen kids, do you think they all had their own bedroom?
As long as the tenants all understand there are lots of others sharing the premises, who is it hurting?
Depending on the culture of the landlord and/or the tenants, this may be nothing unusual.