The proceeds derived from the sale of any bonds, other than refunding bonds, may be used only to pay the cost of acquiring, constructing, improving, enlarging and equipping the project with respect to which they were issued, as may be specified in the indenture or the proceedings in which the bonds are authorized to be issued. Such cost shall be deemed to include the following: the cost of acquiring any interest in the land forming a part of the project; the cost of the labor, materials and supplies used in any such construction, improvement or enlargement, including architect's and engineer's fees and the cost of preparing contract documents and advertising for bids; the purchase price of and the cost of installing equipment for the project, the cost of landscaping the land forming a part of the project and of constructing and installing roads, sidewalks, curbs, gutters, utilities and parking places in connection therewith; legal fees and recording fees and expenses incurred in connection with the authorization, sale and issuance of the bonds issued in connection with such project and interest on the said bonds for a reasonable period prior to and during the time required for such construction and equipment and for not more than one year thereafter.

If any of the proceeds derived from the sale of the bonds remains undisbursed upon completion of such work and payment of all the costs and expenses thereof, such balance shall be used for the retirement of the principal of the bonds of the same issue.