A purchaser under an executory contract of sale who is in possession of land has a qualifying ownership interest for the deduction under 54:4-1 et seq., which provides "... An executory contract for the sale of land, under which the vendee is entitled to or does take possession thereof, shall be deemed, for the purposes of this act a mortgage of said land for the unpaid balance of purchase price ..."
N.J. Admin. Code § 18:27-2.11