In connection with any housing project located wholly or partly within the area in which it is authorized to act, any state public body may contract with a housing authority or the federal government with respect to the sum or sums, if any, which the housing authority or the federal government may agree to pay, during any year or period of years, to the state public body for the improvements, services, and facilities to be provided by the state public body for the benefit of said housing project or its residents; but in no event shall the amount of such payments exceed the estimated cost to the state public body of the improvements, services, or facilities to be so supplied; provided, however, that the absence of a contract for such payments shall in no way relieve state public bodies of the duty to furnish, for the benefit of said housing project and its residents, customary improvements and such services and facilities as state public bodies usually furnish without a service fee.