Before exploring different mortgage options, you Need to know about how lenders review your application and decide Whether to APPROVe historical application for a mortgage. Two main criteria for application. The first is ITS Ability to pay a mortgage. This is Assessed on the Basis of Their total monthly total monthly Income and Debt. In general, Monthly Income to Debt ratio of 36-40% (in total monthly Expenses Do Not Exceed 36-40% of your Monthly Income) is desirable. The second factor is your Willingness to pay, and is Represented by your credit score.