What the Director must do. The principal duties at 12 U.S.C. 4513(a)(1) are to oversee "the prudential operations of each regulated entity" and to ensure that each one operates "in a safe and sound manner, including maintenance of adequate capital and internal controls"; that its activities "foster liquid, efficient, competitive, and resilient national housing finance markets"; that it complies with its statutes and FHFA's rules; that it acts only within its authorized mission; and that it is operated consistently with the public interest. FHFA is a safety-and-soundness and mission regulator. It does not write the consumer disclosure, servicing or anti-kickback rules that apply to mortgages, which come from the Consumer Financial Protection Bureau under the Truth in Lending Act and RESPA.
Conservator since 2008. Under 12 U.S.C. 4617(a) the Director may appoint FHFA "as conservator or receiver for a regulated entity", at the Director's discretion, "for the purpose of reorganizing, rehabilitating, or winding up the affairs" of that entity, on statutory grounds that include assets insufficient for obligations. FHFA has served as conservator of Fannie Mae and Freddie Mac since 2008. That arrangement puts the regulator in the position of directing two companies it also supervises, which is why FHFA announcements often read as decisions by Fannie Mae and Freddie Mac rather than as rules addressed to them. How and when the arrangement ends is a policy question this page does not predict.
The three things a borrower feels. First, the conforming loan limit. The charter acts require the Enterprises' baseline limit to be adjusted every year by the change in a house price index FHFA maintains, and FHFA announces the values each November for loans acquired the following year. For one-unit properties in most of the country the current baseline is $832,750, with higher limits in high-cost areas; how the limit is built belongs to the conforming loan page. Second, the FHFA House Price Index, which FHFA describes as "a weighted, repeat-sales index" built from repeat transactions on single-family homes whose mortgages Fannie Mae or Freddie Mac bought or securitized. The limit itself is adjusted using an expanded-data version of the index. Third, the underwriting rules the Enterprises apply, including which credit scoring models they accept. A borrower never applies to FHFA, but these three outputs decide whether a loan is conforming, how a county's limit moves, and what a lender selling to Fannie Mae or Freddie Mac will ask for.
What FHFA is not. It does not insure mortgages; the Federal Housing Administration, an office inside the Department of Housing and Urban Development, does that, and Ginnie Mae is part of HUD as well. It does not supervise the banks, credit unions and mortgage companies that lend to households. And it is not a source of borrower assistance applications: a homeowner in trouble on a Fannie Mae or Freddie Mac loan works with the loan's servicer, which follows the Enterprises' servicing rules.