The Collaborative International Dictionary of English v.0.48:

halfway house \half"way house`\,
   1. an inn or place of call midway on a journey.
      [1913 Webster]

   2. A residence for former convicts, persons recovering from
      mental illness, or from drug or alcohol addiction, serving
      as an intermediate environment between total confinement
      and complete freedom, and having structured programs
      designed to ease successful reintegration into society.
      [PJC]