It shall be the duty of either the property owner, broker, salesman or agent when selling an unimproved lot or a newly constructed house being sold for the first time, located within a subdivision recorded or intended to be recorded among the county land records, to provide to the purchaser, or if more than one (1) purchaser, to at least one (1) of the purchasers, prior to the entering of a contract of sale, an entire copy of the single recorded plat of subdivision on which the subject property is located or a copy of such plat as it is intended to be recorded in the land records; provided, that this provision shall not apply to subdivision plats not available from the Maryland-National Capital Park and Planning Commission. In the event that the property being sold is not an unimproved lot or a newly constructed house being sold for the first time, the purchaser shall be provided with a copy of the subdivision plat as aforesaid, or in the alternative, the purchaser in writing may waive the receipt of a copy of such plat at the time of execution of the contract, but shall prior to or at the time of settlement, be provided by the property owner, broker, salesman or agent, with a copy of the subdivision plat. (1968 L.M.C., Ex. Sess., ch. 1, § 1.)