Then I turned around and deposited my -$100,000 into the bank, so now my bank balance reads $-184,000.

update: I quit the app and opened it again and now my bank balance is positive. And somehow it has jumped to $171335824. Sweet.

update 2: The fact that you can gain XP by winning a fight on defense seemingly makes the game unbalanced. You can just put all your points into defense and none into attack, and then wait until other people attack you so you can win the fight.