§53-38 Tax exemption. Where and so long as the major portion of a redevelopment project of a redevelopment corporation is composed of residential units and the rents for the residential units are reasonable as compared with prevailing rental levels for comparable accommodations, the land and improvements in the project shall be exempted (1) for ten years from the date of acquisition of such project by the redevelopment corporation, from real property taxes, other than assessments for local improvements in excess of the total real property taxes paid upon the land and improvements for the year prior to the commencement of proceedings by the agency for the acquisition of the lands and improvements; and (2) for the next succeeding fifteen-year period following such ten-year period, from real property taxes on fifty per cent of the assessed valuation of the property and improvements; provided that: