I also considered the land idea and sticking a BOXABL or shipping containers on a plot and building that way.

Sounds to labor intensive and to expensive the first product is 150.00 for 500 sq ft and the second product is 299.00 per 500 sq ft plus 25.00 each shipping.

I can only speak for OKC on a personal level but have friends that pursued Tulsa recently for multi and ended up abandoning ship.

The townhouse is a win for you financially and can be the vehicle that rights the ship. 

Granite shipping is no fun, but the heat resistance and heartiness make-up for it. 

If you're under contract then the ship has sailed and you're stuck. 

Like @Steve Vaughan title loans and CC's are some risky ways to do it but all depends on your risk tolerance.Don't sink the ship for 500 sqft today vs down the road remember RE is a slow game.

Guess it also depends on the cost for you to build it, can't let the ship sink.If they don't have the money to build a ramp, how would they have the money to secure a new home and move?

That ship has sailed now and in my experience it is better to start the eviction process as soon as possible rather than waiting.

Quote from @Dock Newell Jr: "ADU" stands for Accessory Dwelling Unit.