Because if they knew what they were signing, they'd know that as soon as the interest rate started to rise, the monthly payment would also increase, they wouldn't be able to pay anymore and  they would end up without a house.
Porque se eles soubessem o que estavam a assinar, saberiam que assim que as taxas de juro começassem a subir, a prestação mensal vinha por aí acima, eles deixavam de ser capazes de pagar e ficavam sem casa.