This cycle of money supply allows lenders to continue to loan money to homeowners by replenishing the the money the lender loans when FHLMC buys the mortgages on the secondary market.

Freddie Mac is one of two for-profit corporations (the other being Fannie Mae) chartered by Congress to promote homeownership in the U.S. Together with Fannie Mae, Freddie Mac creates a cycle of money supply to the mortgage industry by purchasing mortgage loans from loan originating banks, and resell these mortgage-back securities to Wall Street investors.

There are alternative programs that do not need to be underwritten by LP, DU or DO.

Freddie Mac has also developed Loan Prospector (LP), a loan underwriting engine that automates the risk assessment process of conforming loans. Together with Fannie Mae's Desktop Underwriter (DU) and Desktop Originator (DO), Loan Prospector is one of three most adopted underwriting systems. With the exception of manually underwritten mortgage applications, every conforming loan that is eventually delivered to FHLMC is underwritten with Loan Prospector.

Loans that are sold to FHLMC must be in compliance with the underwriting guidelines promulgated by FHLMC. These Freddie Mac eligible loans are called conforming loans. Because Freddie Mac was founded with the purpose of helping Americans own their own homes, its underwriting guidelines are written to keep the commercial investors and the wealthy from using conforming products to finance multi-million dollar properties. Although there are no purchase price limits, FHLMC caps the maximum loan amounts for each eligible property types. These loan amounts are better known as conforming loan limits. Besides the maximum loan limits, Freddie Mac also sets the eligible property types, and the borrower's credit, income and asset requirements.