Amends the Internal Revenue Code with respect to tax-exempt private foundations to exempt from the excise tax on self-dealing the leasing of office space to such a foundation by a disqualified person for use by the foundation in a building whose other tenants are not disqualified persons, if: (1) such leasing is pursuant to a binding lease in effect on October 9, 1969, or pursuant to renewals of such a lease; (2) the original execution of such lease was not a prohibited transaction; and (3) the space is made available to the foundation on a basis no less favorable than it would be if the transaction were at arm's length.