> Lots of people take loans without precisely knowing where they'll find money to pay them back.

Hell, i'd say in almost all cases that is true. How am i going to know if i'll be at my current job long enough to pay back that car loan? Hypothetically i will have a job, and will pay it back, but in reality i have no idea how i'll pay it back.

At best, i can accurately predict X months of payments. After that, it's all just educated guesses.