You could argue anticipatory repudiation, in defense, if needed…You would want to include an exhibit to your complaint demonstrating the tenants intent, in writing, and supply a very detailed and complete declaration. 

If a foreclosure defense attorney had the owner's best interest at heart, they would have recommended a sale long ago.

I also just received an email from the buyer this morning stating he is holding out this month's payment and future payments in case he needs them for legal defense.

Generally speaking; if a Landlord were to agree or intonate, in those jurisdictions where quantum meruit is allowed, either that there would be some compensation against rent for services rendered; or even if a reasonable person would believe that there would be compensation for services rendered, the landlord can be held liable under the theory.There are some defenses in contract against this; such things as merger clauses.

Tenant screening is your first line of defense being a landlord. 

First born filed Affirmative Defense.

At my house I use Home Defense Max it comes in a one gallon container and it usually last for around a nine months per treatment cheap easy and quick.  

The liability coverage on your condo HO6 policy will pay for your defense costs and settlements up to the policy limit if someone were to sue you for damages incurred inside your unit.

Also, keep in mind your application is the first line of defense, so it could be (like Dracula to a cross or light), the application is doing its job and turning people away--even though they love it.... due to their rental or credit history.  

Rejecting Kentucky's defense of its turf laws on consumer protection grounds, the court noted that "the complete exclusion of a buyer's broker from the transaction may well render the foreign buyer/lessee more vulnerable to fraud.