In the case of a sale of a unit where delivery of a public offering statement is required, a contract of sale may be executed, but no interest in that unit may be conveyed until the declaration is recorded and the unit is substantially completed, as evidenced by a recorded certificate of substantial completion executed by an architect licensed under the provisions of Chapter 83 [83A] of the General Statutes or an engineer registered under the provisions of Chapter 89C of the N.C. Gen. Stat., or by issuance of a certificate of occupancy authorized by law. (1985 (Reg. Sess., 1986), c. 877, s. 1.)