They typically wait until the last minute before they confront the reality that they cannot afford to keep their home.

@Joshua YangA few 'stake-out' nights, or perhaps even confrontational barging in and letting airbnb guests know the situation and that they cannot stay there, and informing them they need to give a 1 star review, will have a huge impact.If you want to go all the way, as well, you might see if you can get law enforcement involved. 

Essentially, if it's not in premium condition, they can warrant a service call and the associated fees.Be careful when you confront them on it because you need to consider their defense.

People get real weird and confrontational when they're selling their homes because they've got their life wrapped up in that house and its hard to separate all that emotion. 

She knows the rental rules pretty well, and she is paying below market rental price.How should I best inform her both humanly and legally and not missing any steps so she would have minimal confrontation from her?  

About a month ago she confronts me with "information" she could have only known if she had gone through my personal belongings.

Raising the rent too high could lead to undesired confrontation and may be difficult to find tenants moving forward if the current tenants choose to find housing elsewhere.

I would directly confront that tenant tell him that is absolutely inexcusable behavior-- if he is month-to-month, I'd 30 day notice him, if is lease is not close to the end, I'd 3 day him and tell him he has 30 days to move and if he wants to fight, his creepy comments can be part of a public court record.

He's been in the game for a minute but doesn't strike me as the confrontational type, so I guess he figured we'd work it out amicably later. 

Also, without being confrontational, bring up their exit in conversation.