The "Affordability and Fairness for Mountain Communities Act of 2025" mandates the Secretary of Housing and Urban Development to establish an Area Median Income Localization Waiver program within 90 days of enactment. This program allows county governments to apply for a waiver to calculate area median income (AMI) for specific federal housing programs using more localized geographic data. Specifically, counties can choose to use a ZIP Code as the calculation area or a group of counties that share a border with the applying county. Upon application, the Secretary is required to grant these waivers, providing counties with the flexibility to use these localized AMI calculations or revert to the original statutory methods for covered programs . These covered programs include various critical housing assistance initiatives administered by HUD and the Secretary of Agriculture, such as public housing, Section 8 rental assistance, the HOME Investment Partnerships program, and supportive housing for the elderly and persons with disabilities. This provision aims to ensure that income eligibility for housing assistance more accurately reflects local economic conditions, especially in areas with significant disparities within a broader region. Furthermore, the bill directs the Secretary to conduct a comprehensive study within two years, focusing on optimizing the use of AMI to support affordable housing in mountain communities . This study will identify alternative AMI calculation methods and metrics to improve affordability for low-income families and evaluate the impact of including roommates in AMI calculations for seasonal workers. The resulting report to Congress will assess the affordable housing crisis in mountain communities, analyze the effects of high housing cost adjustments , and recommend reforms to AMI usage to make housing more accessible for low-income and seasonal workers in these specific regions.