California Code, Code of Civil Procedure - CCP § 1263.730

Where the required action is caused to be performed by the plaintiff, and the amount available to the trustee under this article is insufficient to meet the actual cost incurred by the plaintiff to complete the required action, the plaintiff may either apply to the court for a new hearing regarding identification of the probable cost, or complete the required action at its own expense and bring an action against the defendant to recover the additional costs.