This is probably the most common reason to arbitrage.

But there is a lot of missing info that makes it hard to even begin.As other's noted, it could be any number of things, some more common than others.It might not even be bathroom related, i.e. a roof leak that is showing itself in a bathroom (but presumably this would be present when raining and shortly thereafter).Toilet, could be wax ring or the O ring that connects tank to bowl.  

I love hearing insight from hosts who have solved this common pain point.

Not necessarily hard times, but more commonly life events.

Later, he took common asked qustions from the book tours and wrote another book.

The rest, set aside contingency funds to account for things you think may have been missed, unless its a terrible deal, move on.If the owner doesn't keep Quick books or any other accounting, you won't see a P&L or cash flow statement, so you'll be working off the leases.This is pretty common.  

IMHO it is literally the easiest way for “the common person” to build immense wealth.

A personal residence is an asset by the most common definition. 

Yeah, that commonly happen.

I think so, however the common areas, including exterior, would need to be Lead Free as well.