159.09 Trust agreement.—In the discretion of the governing body, each or any issue of such bonds may be secured by a trust agreement by and between the unit and a corporate trustee, which may be any trust company or bank having the powers of a trust company within or outside the state. Such trust agreement may pledge or assign the revenues to be received, but shall not convey or mortgage any project or any part thereof. Either the ordinance or resolution providing for the issuance of revenue bonds or such trust agreement may contain such provisions for protecting and enforcing the rights and remedies of the bondholders as may be reasonable and proper and not in violation of law, including covenants setting forth the duties of the unit and the governing body thereof in relation to the acquisition, construction, improvement, maintenance, operation, repair, and insurance of the project, and the custody, safeguarding, and application of all moneys. It shall be lawful for any bank or trust company incorporated under the laws of this state, or any other state or territory of the United States, that has a branch or principal place of business in this state as defined in s. 658.12, to act as such depository and to furnish such indemnifying bonds or to pledge such securities as may be required by the governing body. Such ordinance or resolution or such trust agreement may set forth the rights and remedies of the bondholders and of the trustee, if any, and may restrict the individual right of action by bondholders as is customary in trust agreements or trust indentures securing bonds or debentures of corporations. In addition to the foregoing, such ordinance or resolution or such trust agreement may contain such other provisions as the governing body may deem reasonable and proper for the security of bondholders. Except as in this part otherwise provided, the governing body may provide, by ordinance or resolution or by such trust agreement, for the payment of the proceeds of the sale of the bonds and the revenues of the project to such officer, board or depository as it may determine for the custody thereof, and for the method of disbursement thereof, with such safeguards and restrictions as it may determine. All expenses incurred in carrying out such trust agreement may be treated as a part of the cost of operation of the project affected by such trust agreement.