(6) provides criteria whereby the commissioner may act upon applications by owners for increases in excess of the level of fair rent increase established under this law provided, however, that such criteria shall provide (a) as to hardship applications, for a finding that the level of fair rent increase is not sufficient to enable the owner to maintain approximately the same average annual net income (which shall be computed without regard to debt service, financing costs or management fees) for the three year period ending on or within six months of the date of an application pursuant to such criteria as compared with annual net income, which prevailed on the average over the period nineteen hundred sixty-eight through nineteen hundred seventy, or for the first three years of operation if the building was completed since nineteen hundred sixty-eight or for the first three fiscal years after a transfer of title to a new owner provided the new owner can establish to the satisfaction of the commissioner that he or she acquired title to the building as a result of a bona fide sale of the entire building and that the new owner is unable to obtain requisite records for the fiscal years nineteen hundred sixty-eight through nineteen hundred seventy despite diligent efforts to obtain same from predecessors in title and further provided that the new owner can provide financial data covering a minimum of six years under his or her continuous and uninterrupted operation of the building to meet the three year to three year comparative test periods herein provided; and (b) as to completed building-wide major capital improvements, for a finding that such improvements are deemed depreciable under the Internal Revenue Code and that the cost is to be amortized over a twelve-year period