This bill creates a new option for certain first responders to buy into Medicare before age 65. Specifically, it allows qualified first responders who are between 50 and 64 years of age and have separated from service due to retirement or disability to enroll in Medicare Part A, B, and D. Eligible individuals must be U.S. residents, citizens, or lawfully admitted permanent residents, and not otherwise entitled to Medicare benefits. Those who enroll would receive the same benefits and protections as other Medicare beneficiaries, including the ability to join Medicare Advantage plans. The Secretary of Health and Human Services would determine a monthly premium based on the average per capita cost of all Medicare benefits. The legislation ensures that this coverage counts as minimum essential coverage under the Affordable Care Act and makes participants eligible for premium assistance tax credits and cost-sharing reductions. It also guarantees the issue of Medigap policies for these individuals, applying age 50 instead of 65 for certain provisions. An oversight board will monitor implementation, and grants will be provided for outreach and enrollment assistance to help first responders understand and access this new option. Crucially, the bill mandates that the implementation of this buy-in option must not negatively affect benefits for existing Medicare beneficiaries or the solvency of the Medicare Trust Funds.