The vast majority of the empty apartments aren't owned by players but an investment group, at least that was the talk when they all vanished from the auction.
I bought mine for just over 200ped for use as extra storage but there were pages and pages of them. You could pick and choose based on location.
Who owns them is anyone's guess but it might be someone who holds shares in MA or has cash tied up in them.
But would they be breaking their own rules about adding so many apartments at this stage?