“Small housing project” means real property containing or proposed to contain a separate residential structure having not more than four dwelling units and which is owned by an agency and proposed to be conveyed to persons and families of low or moderate income or to private parties pursuant to an agreement with an agency to develop or maintain the residential structure which is proposed to be restricted by a recorded instrument for the use and occupancy of persons and families of low or moderate income for a period of not less than 30 years, or to the term otherwise provided by law, and which meets either of the following criteria: