superrific
Master of the ZZLverse
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None of these explanations are correct. The bank could charge interest and principal at any schedule you and it agree to. You could pay all interest one month, and then all principal the next, and then half/half and then skip two months and have a big 3 month lump sum. So "math" isn't the explanation.
The explanation is that people like to have a monthly payment that doesn't jump up and down. It's also sound underwriting practice (though by no means the only one possible), so the "same payment every month" becomes the boundary condition. AT THAT POINT the math dictates the repayment schedule.
I don't know to what extent regulations require mortgages to be structured this way, but the primary reason that mortgages are standardized is to make them easier to trade on a secondary market. When you know the repayment schedule is standard, then interest rate and LTV is most of what you need to know to get a decent valuation given a particular owner's credit history.
The explanation is that people like to have a monthly payment that doesn't jump up and down. It's also sound underwriting practice (though by no means the only one possible), so the "same payment every month" becomes the boundary condition. AT THAT POINT the math dictates the repayment schedule.
I don't know to what extent regulations require mortgages to be structured this way, but the primary reason that mortgages are standardized is to make them easier to trade on a secondary market. When you know the repayment schedule is standard, then interest rate and LTV is most of what you need to know to get a decent valuation given a particular owner's credit history.