Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

While Facebook Marketplace isn't the sketchiest site (craigslist), I personally would never give my ID across it.

Managing 17 shopping centers and selecting sites for new developments is no small feat—kudos to you!

I'm new here to the BiggerPockets site.

Then you can check AirDNA.co (or similar site). 

Here is a video that runs down the basics - https://s-media.nyc.gov/agencies/specialenforcement/01-Legal...There is also a prohibited building list - https://www.nyc.gov/site/specialenforcement/registration-law...Here are some more info overall - https://www.nyc.gov/site/specialenforcement/registration-law..All of this makes STRs in the city pretty tough but it certainly not impossible.

I found them on sunbiz site when I searched  the company name under fictitious name! 

Would any of you recommend a certain site that specifically handles formation of LLC for rental property?  

You can find owners' names and mailing addresses on the county assessors site.

Either way it would be a grey area, selling a house with a different amount of units/bedroom/bathroom seems extreme though. its an auction site, I have seen auction sites miss the fact there was additional lots in a sale.