The city’s Affordable Housing Trust Fund, has yielded $1 billion since funding began in 2003, public officials said. The $1 billion mark was reached after the latest round of funding, $57 million, was approved by Mayor Antonio Villaraigosa. The fund, begun during the Hahn administration, has so far awarded $207 million to developers, representing 84 projects and 4,892 affordable housing units. Each dollar awarded leverages an additional $4.50 from state and private sources. In 2005, Villaraigosa announced a plan to add another $50 million to the fund. Those funds are earmarked for housing for the homeless.