Many lenders (most) make loans that they will resell to other lenders and investors in the market place. In order to be sold, those loans need to meet stringent guidelines and conform to a specific profile. This is often limiting because perfectly good loan scenarios may have one aspect that does not meet FNMA guidelines. In those cases, the lender of choice would be a portfolio lender, or one that holds its loans in its own portfolio. These lenders can make or break their own rules without having to please someone else.