[header] How to underwrite loans [title] Calculate the borrower's mandatory monthly costs. [step] Payments such as those equal to the proposed mortgage payments, taxes, and insurance comprise mandatory monthly costs. These are costs that are necessary and cannot be compromised or adjusted with ease. 
[title] Determine the amount of debt the borrower must pay off each month. [step] Debts from other loans, such as student loans for example, and revolving debts (credit cards) must be taken into consideration.