No lot shall contain any building used in whole or in part for residence purposes unless such lot abuts for at least forty (40) feet on at least one street, and there shall be not more than one (1) single-family dwelling for such frontage. The Council may also allow, at its own discretion, the construction of a building to be used in whole or in part for residence purposes on a lot which has an exclusive unobstructed private easement of access at least twenty (20) feet wide to a street, for one (1) single-family dwelling, if the Council determines that such construction is not in conflict with the intent of the Zoning Code.