> I don't know how it works in Cali but in most other places if the landlord shares the property (like they themselves are also a tenant) they can be as discriminating as they want.

That's not how it works in California (whether or not it is how it works in some other places); there are limited exceptions for taking on a single boarder and roommate situations, which are described in the page linked from the post you responded to, under the heading "Limited exceptions for single rooms and roommates".