About being homeless from billionaire, well that's their problem if they are not good in handling money
As they call it, from shithouse to penthouse and back again
Personally, I can think of only one kind of a real-life scenario when a billionaire would turn into a homeless person (purely hypothetical cases aside). This may happen when the billionaire in question was either born into wealth and not properly raised ("born with a silver spoon in his mouth"), or was given all that wealth by some strange twist of luck (think lottery or even gambling itself here)
So if that billionaire made himself into a billionaire "from ground up" (think Bill Gates here, though he comes from a very well-to-do family), it is highly unlikely that he will turn into a gambling addict and then move to live under the bridge because this sweet "spot" in his mind is already taken up by something else (most certainly, by that something which made him into a billionaire in the first place)