Where the Minister, as a result of such enquiries as he or she considers necessary, is satisfied that—
(a) an area contains 20 or more houses occupied by low income households;
(b) at least 50% of the houses referred to under paragraph (a) is overcrowded or so arranged as to be congested or unfit for human habitation and not capable at a reasonable expense of being rendered so fit;
(c) it is expedient in relation to the provision of housing accommodation for lower income persons that the area as a whole be redeveloped,
the Minister shall cause the Corporation to prepare and submit for his or her consideration a plan defining the area.