The law limits the total amount that the landlord can require you to pay as a security deposit. The total amount allowed as security depends on whether the rental unit is unfurnished or furnished and whether you have waterbed.
Unfurnished rental unit: The total amount that the landlord requires as security cannot be more than the amount of two months' rent. If you have a waterbed, the total amount allowed as security can be up to two-and-a-half times the monthly rent.
Furnished rental unit: The total amount that the landlord requires as security cannot be more than the amount of three months' rent. If you have a waterbed, the total amount allowed as security can be up to three-and-a-half times the monthly rent.
Plus first month's rent: The landlord can require you to pay the first month's rent in addition to the security deposit.69
http://www.dca.ca.gov/legal/landlordbook/when-rent.htm#rulesgoverningsecuritydeposits