Contract for payments for services. 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 commission, housing authority or the federal government with respect to the sum or sums, if any, which the housing commission, 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 furnished by it for the benefit of said housing project, 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 furnished: Provided, however, That the absence of a contract for such payment shall in no way relieve any state public body from the duty to furnish, for the benefit of said housing project all such services and facilities as such state public body usually furnishes without a service fee.