The code official or housing inspector shall issue a rental housing license for each dwelling, dwelling unit or rooming unit, when upon inspection finds such unit meets or exceeds the minimum requirements set forth by this chapter; also a rental housing license shall be issued for each dwelling, dwelling unit or rooming unit, when a variance has been granted by the Board of Appeals; provided, however, it is found that no condition exists, in a shared or public area of the building or in any other part of the unit, which could endanger the health or safety of the occupants of such unit or of the public. Such license shall show the number of occupants for which the dwelling, dwelling unit or rooming unit is approved for and once issued shall remain valid until it expires or such time as the code official or housing inspector determines that the dwelling, dwelling unit or rooming unit does not meet the minimum requirements set by this chapter.