Rural Broadband Financing Flexibility Act This bill provides tax incentives for investment in broadband, particularly in rural areas. Specifically, the bill allows issuance of private activity bonds for financing qualified broadband projects, issuers of broadband infrastructure bonds a credit for interest payments under such bonds, and a 10% investment tax credit for qualified broadband projects. The bill defines qualified broadband project as any project that (1) is designed to provide broadband service solely to one or more areas that are rural areas and in which more than 50% of residential households do not have access to fixed, terrestrial broadband service that delivers at least 25 megabits per second downstream and at least 3 megabits service upstream, and (2) results in gigabit capable internet access to certain residential and commercial locations.