Cal. Civ. Code § 1950.8

(a) This section applies only to commercial leases and nonresidential tenancies of real property.
(b) It shall be unlawful for any person to require, demand, or cause to make payable any payment of money, including, but not limited to, “key money,” however denominated, or the lessor’s attorney’s fees reasonably incurred in preparing the lease or rental agreement, as a condition of initiating, continuing, or renewing a lease or rental agreement, unless the amount of payment
is stated in the written lease or rental agreement.
(c) Any person who requires, demands, or causes to make payable any payment in violation of subdivision (a), shall be subject to civil penalty of three times the amount of actual damages proximately suffered by the person seeking to obtain the lease or rental of real property, and the person so damaged shall be entitled to an award of costs, including reasonable attorney’s fees, reasonable incurred in connection with obtaining the civil penalty.
(d) Nothing in this section shall prohibit the advance payment of rent, if the amount and character of the payment are clearly stated in a written lease or rental agreement.
(e) Nothing in this section shall prohibit any person from charging a reasonable amount for the purpose of conducting reasonable business activity in
connection with initiating, continuing, or renewing a lease or rental agreement for nonresidential real property, including, but not limited to, verifying creditworthiness or qualifications of any person seeking to initiate, continue, or renew a lease or rental agreement for any use other than residential use, or cleaning fees, reasonably incurred in connection with the hiring of the real property.
(f) Nothing in this section shall prohibit a person from increasing a tenant’s rent for nonresidential real property in order to recover building operating costs incurred on behalf of the tenant, if the right to the rent, the method of calculating the increase, and the period of time covered by the increase is stated in the lease or rental agreement.