The "Build HUBS Act" seeks to alleviate the national housing crisis by expanding and streamlining federal financing for transit-oriented development (TOD) projects. It extends the authorization for the Transportation Infrastructure Finance and Innovation Act (TIFIA) program and the Railroad Rehabilitation and Improvement Financing (RRIF) program from fiscal years 2027 through 2031. The bill introduces new definitions for attainable housing projects, which serve households up to 120% of the area median income with a majority of units affordable to those at 80% AMI, and for transit-oriented development projects, located near transit facilities and generating new revenue.

To facilitate financing, the bill allows for an investment-creditworthiness assessment alternative for TOD projects, moving beyond the strict requirement of an investment-grade rating. This alternative includes options like joint liability agreements, alternative ratings for smaller projects, or certification by an approved originator-servicer. For attainable housing projects, at least 75% of TIFIA assistance must be used for residential components, and loans under both TIFIA and RRIF will have a reduced interest rate of half the Treasury Rate.

The legislation establishes delegated origination and underwriting programs for TOD projects under both TIFIA and RRIF, modeled after HUD's Multifamily Accelerated Processing system. These programs allow qualified third-party servicers to handle loan origination and underwriting, significantly reducing processing time and administrative burden. Projects financed through these delegated programs are explicitly exempt from the investment-grade rating requirement.

Furthermore, the bill streamlines environmental review processes for TOD projects by exempting land acquisition activities from NEPA prior to application and establishing categorical exclusions for certain activities like office-to-residential conversions or new commercial construction on disturbed land. It also mandates public disclosure of fee structures and comprehensive guidance on eligibility requirements for TOD projects. A savings provision clarifies that the Act does not preempt State or local zoning laws.