The incidental costs of issuing the refunding bonds may be paid by the purchaser of the refunding bonds or may be paid from any other legally available source including, without limitation, the general fund of the local agency, other available revenues of the local agency under the control of the legislative body, the proceeds of the sale of the refunding bonds, the interest or other gain derived from investment of any of the proceeds of the sale of the refunding bonds, any other moneys in escrow or in trust, or any combination thereof, as the legislative body may determine.