According to the Housing Census of Statistics Korea, as of 2019, unoccupied units in multifamily housing that are more than twenty years old account for one-third of the total unoccupied houses, and are expected to increase more rapidly. Unoccupied units in old multifamily housing feature complicated characteristics due to unique aspects of multifamily housing (i.e., exclusive area, common area, partitioned ownership) in addition to housing deterioration and vacancy. Since multifamily housing requires each unit to share responsibilities regarding building maintenance, the non-payment of maintenance fees by owners of unoccupied units and neglect of maintenance may undermine the residential environment drastically.