For the purpose of this article, the following terms shall have the following meanings:

1. 1. "Residential structure" shall mean a one or two family dwelling or a single unit of a multiple dwelling, including an individual condominium unit or cooperative unit, which is offered for sale or rental on or after January first, nineteen hundred eighty-one by any person other than the original contractor or builder of any such dwelling.
2. 2. "Heating and/or cooling bills" shall mean all bills rendered by a retail vendor for energy used for heating and/or cooling purposes in a residential structure, including any bills where the cost of energy used for heating and/or cooling purposes is not differentiated from the costs of energy used for any other purpose.
3. 3. "Lessor" shall mean any person who offers any residential structure for lease to the general public.
4. 4. "Seller" shall mean any person who offers a residential structure for sale to the general public.