Much better than a legal filing or media attention. 

Your client should consult a real estate attorney to draft an agreement with the ex and ensure there are no legal or tax issues, especially since this is an investment property.

Is there any legal action one can take or is it just a lost cause?

Seek legal advice, however, what I understand is that there are really two way to wholesale that is legal in the state of Arkansas.

In total, including money lost from rent, legal fees, and repairs, the situation cost almost $30k.

Or a legal perspective?

It may be a tough pill to swallow if you feel you’re totally right, but you may be surprised at the LEGAL opinion rendered by counsel.  

The real prohibitive costs come from the legal, compliance, and reporting requirements of registering a security.

It seemed like most the folks you have on staff are CPA or other, but no specific legal experts.

The seller has the two lots legally separated, but due to deed restriction imposed by the subdivision development, found that building a house on the “tennis court” lot was not allowable.