Not enough to fix the housing problems CA has. Not nearly. And if that's the problem, tax empty homes.
But even then, even if there are empty homes, building more will still fix the problem. Let those foolish owners leave the homes empty- we can build more anyways.
I really dislike the notion of clearing more land and putting up more cookie cutter houses and apartments for the sake of saturating the housing market in order to get people to rent for reasonable prices.