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 si hubiesen sabido lo que estaban firmando, habrían sabido que si la tasa de interés subía, el pago mensual también se incrementaría. Es decir, ellos no podrían pagar y terminarían sin su casa.