Upon transfer of title to a new owner or execution and recording
of a mortgage, or upon said building becoming vacant, no two-family
dwelling or mixed occupancy containing two or more families and no
multiple dwelling shall be occupied, in whole or in part, until the
issuance of a certificate by the Commissioner of the Building Department
that said dwelling conforms in all respects to the requirements of
this code. The head of the Department may, on the request of the owner
or his certified agent, issue a temporary certificate of occupancy
in his discretion.