California - Can Tenant's Security Deposit be used to pay unpaid rent?

[Tricia O'Brien]

Hello!  My realtor recently told me that it is illegal to use a tenant's security deposit to pay unpaid rent.  He says the security deposit is only supposed to be used to pay for damages to the property. Is this true?? 

I looked up the law related to security deposits , California code 1950.5.  I found it on :  leginfo.legislature.ca.gov.  

It seems to say that one of the things a security can be used for is "The compensation of a landlord for a tenant's default in payment of rent. " 

What do you all think? 

 This realtor  recommends, for tenants without a verifiable rental history (like young adults who have only rented from their parents), you should collect at move in: the first month's rent, the security deposit, and the last month's rent. That way if they don't pay, you can use the "last month's rent" to pay yourself while you are evicting them.  If you collect a double security deposit, you cannot dip into that security deposit to pay yourself for that last 2-3 months of rent while you are evicting them and they are not paying rent.

Any replies would be appreciated! :)