Cal. Gov. Code § 53363.7

The designated costs of issuing the refunding bonds, as defined by Section 53363.8, may be paid by the purchaser of the refunding bonds or may be paid from any other legally available source, including any available revenues of the legislative body, the proceeds of sale of the refunding bonds, the interest or other gain derived from the investment of any of the proceeds of sale of the refunding bonds, or any combination thereof, as determined by the legislative body. However, any amounts paid by the local agency other than from the proceeds of sale of the refunding bonds or from interest or other gains derived from the investment of the proceeds of sale shall be added to the total interest cost to maturity on the refunding bonds in determining whether the issuance of the refunding bonds complies with Section 53362.5.