The owner is remote, and there is one main person running the business locally, so the challenge is how to replace this local person without losing existing business/clients (no, this person is not looking to stay for the long haul).You all sound like very experienced managers. 

There is also a house onsite that the current owners live in and manage the business from.

In almost any city with a large enough population owners can build a permitted ADU on any residential lot.

Are there any sites you use to find owners open to subject to?

in NYC some owners are known to rent out their semi basement which is on a grey side. so during inspection would that cause any issue?

I pulled owner-build permits and acted as the GC which helped me save a ton on construction costs. 

Subject To is a loaded gun, you need safety training.

One of the biggest concerns for both the owner and the property manager like myself, is getting paid.Many guests book for much longer than 30 nights.

I have helped owner occupants use down payment assistance programs to cover the 5% down payment (in MO), and then negotiated seller paying all the closing costs.

I was talking with the owner of a mobile home park within 45 minutes of my home; he inherited it from his father.