The plaintiff in the action shall establish:
(a) that such delinquent taxes remain due and unpaid at the commencement of the action,
(b) that the collector has exercised due diligence to collect such delinquent taxes, and
(c) that he verily believes that such real property is income-producing, or, if the property is not income-producing, that it can be leased and thereby made to become income-producing, and that the collection of such delinquent taxes can be made through a receivership of the rents and income from such real property.
A verification of the complaint in the action shall be prima facie evidence of the facts therein stated.