Quote from @Derrick Lewis: I looked up NY state law just for fun and found a good list of recommended practices.

Does anyone have any practical experience with similar situations and if so what was the outcome and how long did it take to resolve everything?

There are a high number of CPA firms that do not want to get involved outside of the FYI to their clients, and some state boards are saying that a CPA advising related to this registration is an "unlicensed practice of law" given it is not under Title 26 - income taxes - the only place where CPAs and EAs are specifically authorized to interpret law. 

membership is something like APPL which is just non regulated group of private investors working on best practices but there is no authority behind them like  state license or NMLS registration has ..

We both know the numbers you used (mostly that 1000% return number) aren't practical, but humoring them paints an interesting picture about the financial advantage of leverage.

Seller Financing I am the buyer with 30 days to purchase the property and want to simultaneously market it as rent-to-own,  how can I structure the process effectively:Can I structure the deal this way, so I can secure a tenant-buyer while working to close on the home myself,  minimizing my risk and creating a win-win situation.

These books are filled with practical advice to help you avoid these mistakes that start small and snowball into major issues.

This is not a great practice.

My cost to build a 900 sf to 1,200 sf container home is about $90 / sf and that cost comes down in a production environment where materials can be purchased in quantities and the workforce is working on a standard floorplan with multiple units in process simultaneously.

Basically if you are selling/buying a house that has been retrospectively licenced then that part for private use is ok, however if officially and practically if you wish to rent the place out on LTR or STR you are not allowed to ever use this space as part of your rental.