Legal Question in Real Estate Law in California

Sure. And you can legally ask him for a copy of his latest statement from his mortgage showing his mortgage is current. I can legally ask you to give me a million dollars, for that matter. Of course you would be nuts to do so, and while I'll stop short of questioning your sanity if you were to give this potential landlord all this information, if I were you I wouldn't. The best way to deal with potential landlords is to show up with a thick wad of $100 bills to pay the first month's rent and security deposit.

Of course. You have to qualify financially to convince him to rent his place to you.

Certain interview subjects are taboo in job and rental discussions, but as it is still perfectly legal to discriminate against people who can't pay their rent in favor of those wo can, financial questions are OK to separate the creditworthy from the bad risks. Of course, at some point the questions can become unnecessarily detailed. At that point, the prospective tenant may simply decline to answer. It's possible that if a landlord's questioning has become this nitty-gritty, the landlord may have already detected some problem.