In establishing the upper income limits for a family of limited income, the Secretary shall consider factors including: the income of the family available for housing; the size of the family; the cost and condition of available housing; the ability of the family to compete in the private housing market; and standards and definitions established for federal housing programs. The limits established under subsection (a) of this section may vary for different: types of housing; programs of the Administration; and areas of the State. A limit established under subsection (a) of this section may be supplemented for a particular project.