At some stage in the not too distant future, in an overpopulated futuristic earth, every town and city will have several out-of-town 'holding zones' where they can store all the unwanted elements of society. People will be rounded up and placed into these holding zones and kept out of the way. There won't be any bars on the windows, the people won't be locked in little cells, and they'll be free to come and go as they please. They will even be allowed to have visitors at any time of the day or night, but it will still be a 'holding zone' where they will be expected to remain.
These zones will have an important role to play. In years to come housing will be dilapidated and overcrowded, homeless people will fill the streets and food will be scarce; most of the people will survive on rations produced by local councils. The holding zones will prevent the majority of their occupants from roaming the streets with each individual placed into their own little unit within the complex. The majority of the zones will be filled to capacity but there will always be an abundance of people placed on to the 'waiting list' to fill any of the vacancies that arise.
When a unit does become empty there will be a rapid response team ready to come and prepare it for the next person. They will clear away the body and any meagre possessions that the individual may have accumulated, and over the next few days they will prepare the unit for its new occupant. Then the cycle starts all over again. Someone else will play the waiting game - waiting for their own time to come. The holding zones will always have a quick turn-over.
That 'not-too-distant future' is not as far away as you might think though, these places already exist. Only at the moment they are not called 'holding zones', they are called 'retirement homes'.