My sister was suggesting I pay to clear off the existing run-down trailers and get my investment back in land equity.

They would grandfather in any existing homes that are licensed.  

Apparently it doesn't matter as they won't take any new ones, only renewal of existing.

Unlike STRs, a platform that analyzes vacancy, pricing, etc. does not exist. 

From my experience buyers typically prefer these lots because they will not have any neighbors directly behind them.I can't tell from your question if there is an existing house built, that you are purchasing, or if you are buying a lot and going to build on it.Also, you should have access to an interactive flood plain viewer to look where the 100, 500 and zone X for the flood plain are situated.

That would hurt the existing tenants who get kicked out! 

There's a really strong investor community which tends to be a great way to spread the word about existing Airbnbs coming for sale. 

When you purchase a home "subject to" the existing financing, that is when a mortgage stays in the sellers name.

You are pulling strong equity out of an existing property to invest very far away, for the first time, and with limited to no contacts in the area.

A true free market doesn't exist as far as I know.