I think that the credit is built by taking on debt and then paying it down. It shows that you can produce money reliably when required to do so, and that given

I think that the credit is built by taking on debt and then paying it down. It shows that you can produce money reliably when required to do so, and that given some rope, you won't hang yourself with it. Extrapolate that a bit and you're paying a mortgage using the same skills.