(2) own any property, improved or unimproved, or any mortgage or other lien thereon, within any section of a municipality included in a map showing sections containing areas for clearance, replanning and low rent housing, adopted by the planning commission of the municipality as a whole or part of the master plan, or
(3) own any property, improved or unimproved, or any mortgage or other lien thereon, within any section of a municipality which may be designated by the planning commission or the housing authority of the municipality as substandard or insanitary, may sell such property, mortgage or lien, and may, notwithstanding any other provision of law, receive and hold in exchange therefor securities issued by a corporation owning or acquiring title to such property, if such corporation shall agree in writing at the time of such sale, to reconstruct, improve, alter, repair or demolish such property or to construct a new building on such property, or on such property and on any contiguous property owned or to be acquired by such corporation.