In the operation or management of state-aided low-rent housing projects an authority shall at all times observe the following requirements with respect to rentals and tenant selection:— (a) It shall rent or lease the dwelling accommodations therein only at rentals within the financial reach of persons and families of low income. (b) It shall rent or lease to a tenant dwelling accommodations consisting of the least number of rooms which it deems necessary to provide safe and sanitary accommodations to the proposed occupants thereof, without overcrowding. (c) It shall not accept as a tenant any person or persons whose net annual income at the time of admission, less an exemption of one hundred dollars for each minor member of the family other than the head of the family and his spouse, exceeds five times the annual rental, including the value or cost to them of water, electricity, gas, other heating and cooking fuels and other utilities, of the dwellings to be furnished such person or persons. For the sole purpose of determining eligibility for continued occupancy, it may allow, from the net income of any family, an exemption for each minor member of the family (other than the head of the family and his spouse) of either (1) one hundred dollars, or (2) all or any part of the annual income of such minor. For the purpose of this section, a minor shall mean a person less than eighteen years of age or a full-time student between the ages of eighteen and twenty-one years of age. (d) It shall not accept as a tenant in any project any person who is not a citizen of the United States; provided, however, that aliens who have served honorably in the armed forces of the United States, and who have been honorably discharged therefrom, shall be admitted to occupancy if they have made