you do not need one but you certainly want to use some sources that I believe that they have on this site which are a source to check on credit, criminal records and always check resources provided. 

TC charges $19.95 for a background check that includes credit score, evictions, criminal, sex offender registry). 

Real life criminals don't waste the precious seconds or minutes it takes to pick locks.

Dept. of Justice has advocated to sellers/buyers for many years.

However, landlords may terminate a month-to-month tenancy with a 20-day notice if the tenant has violated the terms of the rental agreement, committed a nuisance, or engaged in certain criminal activities.Under the state's "just cause" eviction law, which applies to tenancies in Seattle and some other cities, landlords may only terminate a tenancy for specific reasons, such as nonpayment of rent, violation of the lease agreement, or a landlord's desire to sell or occupy the property.

The so called Housing Justice Project might give you some info also, but also not up to date.

My advice, buy them off now with cash for keys before it turns into 9 months of legal fighting and delays resulting in foreclosure for you.California hates landlords and the courts do their best to delay evictions as much as possible.One by one you will be accused of being a slumlord,racist,sexist,homophobic,and just plain criminal and the liberal judges will eat it up even though they can't prove anything.Every charge against you will result in 60 days of free rent while waiting to get into a courtroom and argue your defense.This is why I will never own rental property in "Blue States"!!

I will only do 1-1 showing for a fully qualified applicant(application, income, credit and criminal background check).

Just be sure to get one that gives a credit, criminal, eviction check. 

Why any of these guys are listened to with anything but disdain is beyond my comprehension.Respectfully,Gary   In America (left wing narrative), there's always self-generated issue that's almost always 'man made', such as these "global warming", or "animal cruelty so lets not eat animal product" or "same toilet for every gender" while they are ignoring the very first problem that people facing like "rising criminality" and "rising violence in highschool".