Upon payment to the treasurer of the purchase price by the successful bidder, the obligations shall be delivered, and the treasurer shall account for the receipt and disbursement of the proceeds thereof for the use named in the resolution or other instrument or instruments authorizing such obligations, in a separate fund or account in the official financial records of the municipality. Pending such use the proceeds may be invested and reinvested in accordance with law, and the income and gain therefrom shall be held as part of the proceeds and applied to such use or to the payment of the obligations and interest thereon or otherwise as provided in any city charter or any other law. The purchaser shall not be obligated to see to the application of the purchase price. When the use authorized is the acquisition or betterment of any land, easements, buildings, structures, machinery, or equipment, the proceeds may be used to pay all expenses, incurred and to be incurred, which are reasonably necessary and incidental to such acquisition or betterment, including, but without limitation, the cost of necessary professional planning studies to determine desirable locations, architectural, engineering, legal, financial advisory, and other professional services, printing and publication, and interest to accrue on the obligations prior to the anticipated date of commencement of the collection of taxes or special assessments to be levied or other funds pledged for the payment of the obligations and interest thereon. When the obligations are payable wholly from the income from a utility or other project, for the acquisition or betterment of which the obligations are issued, the proceeds may be used in part to establish a reserve as further security for the payment of such principal and interest when due. If the contemplated use be afterward abandoned, or if any balance of the proceeds of the obligations remains after the use is accomplished, or if the governing body determines that at least 85 percent of the cost of the use has been paid or finally determined and retains in the fund an amount sufficient to pay the estimated costs of completion, the remainder of the fund may be devoted to any other public use authorized by law, and approved by resolution adopted or vote taken in the manner required to authorize bonds for such new use and purpose. Any balance remaining after the improvement has been completed and paid for, unless devoted to a new use as herein authorized, shall become a part of the debt service fund of the municipality.