Fannie Mae is a financial company whose primary mission is to support a secondary market for mortgages. We review Fannie Mae's business model and explain a role financial analytics play in supporting the business. As an example of such analytics we focus on credit and prepayment models. We explain the importance of these models, describe their basic features and demonstrate some of their real-life elements. We also analyze computational challenges the models create, and describe ways to deal with these challenges. Finally, we overview some elements of a financial analytics software system.