 From Member Station KQED, Dana Cronin explains. The new law makes it illegal for landlords to charge more than one month's rent for a security deposit. Previously, landlords could charge up to three months' rent. San Francisco Assemblymember Matt Haney penned the legislation, which he says will especially help lower-income residents who are often stuck in unsafe or inconvenient living conditions because they can't come up with enough money for a deposit to move elsewhere.