Check local regulations.First, verify that your local zoning laws, HOA rules, or condo bylaws permit renting your property.2.

First thing to do is check with the city or county to make sure the ADU would be permitted to be a STR.

For instance, in New York State, it's not permitted to collect last month's rent, additional security deposits beyond one month's rent, or pet deposits.Regarding the carpet issue, even tenants without pets can sometimes leave carpets in less-than-ideal condition after a couple of years.

Rethinking density limitations like building height, parking requirements, and ADU permitting would be more impactful. 

You know how to get your permits.

Timing your permits and applications might be tricky.

Duplex have different zoning that may permit additional units.

Will I still be permitted to file an affidavit of memorandum EVEN THOUGH my closing date has now come and gone and I am technically in breach of contract?

Plus they are just lovely to work with.And yes a 15 year veteran in both residential and commercial construction, we pull permits. 

I have done everything the right way, the ethical way, treating people with honesty and respect.. treating the market and the process with respect (not cutting any corners, permits, etc) and it seems like I have been beaten down at every turn and now I am at risk of losing everything I have worked hard for years to obtain.