3 U.S.C. § 102 : US Code - Section 102: Compensation of the President

      The President shall receive in full for his services during the
    term for which he shall have been elected compensation in the
    aggregate amount of $400,000 a year, to be paid monthly, and in
    addition an expense allowance of $50,000 to assist in defraying
    expenses relating to or resulting from the discharge of his
    official duties. Any unused amount of such expense allowance shall
    revert to the Treasury pursuant to section 1552 of title 31, United
    States Code. No amount of such expense allowance shall be included
    in the gross income of the President. He shall be entitled also to
    the use of the furniture and other effects belonging to the United
    States and kept in the Executive Residence at the White House.