A conventional mortgage loan is a type of mortgage in which the underlying terms and conditions meet the funding criteria of Fannie Mae and Freddie Mac. About 35-50% of mortgages, depending on market conditions and consumer trends, are conventional mortgages. In other words, Fannie Mae and Freddie Mac guarantee or purchase 35-50% of all mortgages. Conventional mortgages may be fixed-rate or adjustable-rate mortgages. Conventional mortgage loans are typically only an advantage to borrowers with outstanding credit scores and low debt to income ratios.