Take individual property owners to court on individual complaints, don't punish a whole market of potential landlords. 

No response after the 3 days, move toward an unlawful detainer. 

The only way out out is Unlawful Detainer and the so-called squatter / trespass approach rains down on the owner, not the squatter.Bottom line, you have to know your State's Landlord / Tenant regulations and it's painful to do so after the fact.

I issued a 5 day pay or quit on the 9th and I am prepared to get a unlawful detainer once the 5 day period has expired.

Committing mortgage fraud would be a pretty big thing stopping them, but I guess if something that can carry severe legal punishment up to felony isn't stopping them then by all means. . . .

That is in a jurisdiction with a far less driven approach to crime and punishment than is seen in many other places.

The Board of Directors of a Condo Association for individually owned condos, is drafting a policy to require any activity they consider renovations, to be approved by the BoD and any violation of that approval process is punishable by fines. 

Doing so will be an act of punishing the old buyer which is illegal.

I just call myself a "glutton for punishment"!

I am going on a decade working for a large bank, and yes credit worthy borrowers get punished in downturns as the bank tightens policies.The funny thing is banks seem to never learn from the past.