"landlord" Was Actually A Tenant Who Hadn't Paid Rent For 6 Months

Hi, a relative of mine (B) moved into a townhouse around August last year. He found the listing on fb marketplace, for a bedroom inside a townhouse for 900/month, no deposit and no utilities. He got in touch with the "landlord" and on the same day moved in. Was given keys without any deposit.

He informed me this morning that he woke up to the sherif at his door along with the actual landlord, who explained the situation. Apparently the "landlord" who rented him the place was actually a tenant, and this person hadn't been paying rent since August, when B moved in. My relative cooperated and left, with only a backpack packed with essentials. The rest of his things remain there, and I believe he has 2 weeks to get it all gone from the property.

I am just looking for anything that might help his situation. This can't be legal, how does the guy just get to pocket my relative's money? Is there anything he can do to help his situation? He is homeless now and was unaware of the situation until this morning. This is in CA, la county.

I'd also like to add just for clarity that I told him at the time it seemed suspicious that the landlord wanted no deposit and wanted him to move in the same day they met, no background check. But I guess he was on hard times and desperate for a place.

Thank you in advance