I work in property management in So Cal.
Because we are a bussiness this may not be of help to you.
If a vendor has no proof of WC (Worker's Comp) insurance, our company pays
the vendor 6% less and pays the WC in case they get injured.
I'm at the job site so I don't know how it is done in the front office.
The person can also work through someone elses license/insurance someone
they know.
That contractor will bill you and you'll pay a little more.
Good luck
Terry