John is an accountant. He uses the cash method of accounting for federal income tax purposes. In 2019, he performs an audit of XYZ Corporation and charges $15,000 for the audit. Because of XYZ's precarious financial conditions he requires XYZ to issue in 2019 to John a $15,000 secured negotiable note with a fair market value of $11,000. In 2020, John collected $15,000 on the note. How much if anything does John include in taxable income in 2019 and 2020 related to his audit work for XYZ? Please explain.