FHFA will have the burden of proof to establish the existence or amount of the debt. Thereafter, if the debtor disputes the existence or amount of the debt, the debtor must prove by a preponderance of the evidence that no debt exists, or that the amount of the debt is incorrect. In addition, the debtor may present evidence that the terms of the repayment schedule are unlawful, would cause a financial hardship to the debtor, or that collection of the debt may not be pursued due to operation of law. The hearing official shall maintain a record of any hearing held under this section. Hearings are not required to be formal, and evidence may be offered without regard to formal rules of evidence. Witnesses who testify in oral hearings shall do so under oath or affirmation.