With all this said, to answer your question of how you'd value this for a sale, I'd get a STR specific broker that's able to market your property as a turnkey STR with data on the rents, figures, etc.

What percentage of sellers are still contributing in some way, do we have data or knowledge of this?

+1  Real Estate Investing Data and How-to Guides - This here shows that you can filter to Multi family but I don't see it as an option as well.

You can always get MLS data many places.You be the investor, let the realtors do their jobs.

And if your selling NON mls props its hard to run data..

The rental market here seems to be cooling and it's hard to pencil deals even if I rent by the room to achieve higher than average rents.

Looking for guidance on options. new builds aren't hard to finance and I would argue they are preferred to existing fix and flip loans, especially if you have experience. banks look at your experience, your builder's experience, loan structure, permits, etc you need to get an experienced builder familiar with advanced underwriting and negotiations with local, regional, and national lenders. in columbus we do ground up construction for clients at a 20% discount so they can BRRRR out of the new build with equity and we have pages and pages of data on what we build and why and it's all supported by market statistics. 

Then research local regulations and tourism and data. 

You should check if the bank feeds work with your bank otherwise, it's a deal breaker unless you don't mind manually doing the data entry.

This is often achieved with written documentation, such as a formal ROW request from TxDOT or other correspondence indicating that condemnation proceedings were possible if no settlement was reached.