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.
왜냐하면 만약 그들이 서명한  내용을 이해했더라면 이자율이 오르자마자,  임대료도 오르리란걸 알았을테고 더 이상 돈을 지불할 수 없었을테고,  집을 사지 못했겠죠.