Improving transit access for people in low-income communities is an important consideration for transit providers. However, there has only been a limited amount of research on the transit accessibility of affordable housing units. This paper aims to develop a method for evaluating the transit equity of existing affordable housing units and propose easy-to-implement modifications to local bus services to increase transit accessibility levels (assuming housing locations do not change in the short term). The proposed method has three steps, and it is applied to three cities in Tennessee with primarily bus-based transit systems. The first step measures the transit accessibility of specific affordable housing locations and citywide transit accessibility levels using a web-based platform built using open-source software. The second step evaluates the transit equity of affordable housing programs at the city level using Lorenz curves and Gini coefficients, and the transit equity of specific affordable housing locations by proposing a simple inequity index. The results reveal that the level of transit equity for affordable housing units differs across housing programs and cities. In the third step, an example of a modification to a local bus route is evaluated for one affordable housing location with a high inequity index to demonstrate the applicability of the method. The substantial increase in accessible jobs after modification, from 135 to 6,400, highlights the potential effectiveness of implementing short-term transit service changes to improve the accessibility of existing affordable housing locations. This three-step method primarily relies on open datasets that are also available for other regions in the U.S.A.