Typically, a lender originates a mortgage and then turns around and sells it on the secondary mortgage market. Conversely, a portfolio loan is when a lender originates the loan intending to keep it rather than sell it. There is a set of standards and requirements that must be met to sell on the secondary market. The originator who intends to offload the mortgage must abide by these general requirements and standards. If they intend to keep it as a portfolio loan, they can set the terms to whatever they wish, often in a manner favorable to the borrower.