Your irresistible offer appears to not have turned out so well either by your own admission and my advice is to help you and others reading this about the importance of knowing how and what to have in your contracts, how to properly vet buyers BEFORE you bring them a deal, etc. your situation is a great learning lesson for others and for yourself if you are willing to learn from your own mistakes.As to the assignment being legal or not, I am not 100% knowledgeable on NC laws, however, I have had several experienced investors tell me North C has similar laws regarding this process as does CA, FL, etc.

See if you can just repaint the cabinets and install new countertop. 

I own several rentals in Linden with a mixture of AC installed vs not installed.

The key to having great financial systems is the setup and systems: If you get everything structured properly up front, you avoid most of the ugly problems many RE investors face later on.I'm not an accountant nor a bookkeeper, but I have great recommendations for both!

Take ownership of your mistake and learn to do the proper due diligence recommended above😊

However, the fam member installing them for me is only a licensed HVAC contractor in FL so he's been unable to buy the units at the regular retailers that would regularly sell it to him (like Bryant, Johnstone Supply, etc).  

I’m looking for a checklist of everything to buy and do - from installing a smart lock to stocking kitchen basics.

He will be required to have references and proper insurance but it's not difficult having him approved. 

Although, I had done some due diligence in the process of receiving, installing and the actual benefit of the systems.

I find this level of underwriting lacking with many flippers as well, failing to properly consider the holding costs, insurance costs, taxes, etc.