As a rule, these loans have not met the borrower credit requirements of “A” or “A-” category conforming loans. Because mortgage lending is divided into various credit grades, several factors influence whether you receive, say, a “B” or “D” designation, including past credit history, documentation, and your debt-to-income ratio. The more serious a borrower’s problems, the lower the grade of the loan and the higher the rates and fees associated with the loan.