Inventory in Austin is low and cash buyers are a plenty so finding them is going to be difficult but I will definitely ask every one of them if they are open to it...Is it worth giving them a rate that is between banks and hard money (say 8% ) for the first year or so to entice them?

The down side I will say that you will find that this may be an ongoing project as you will constantly need to maintain communication and entice private SDIRA holder to continue to participate with your promissory-note-investment syndication, assuming your lead generation on mortgages to buy stay consistent. 

I have another search service that can pull in public information, and in that service when searching under the name of my subject of interest property's owner, since he was a builder/developer in the area; there was 12 properties that he either purchased or sold and only one or two of them listed a 3rd party lender (mortgage), and neither was related to the property of interest.Short of flying there to visit the county recorder's office (called Superior Clerk of the Court in this locality/state), or enticing a local realtor to do some research for me (and hoping they don't take my deal away from me, when they realize this could be an opportunity for them as an investor versus being my agent)...what else needs to be done to definitively track down mortgage or title information on this building?

That not only ensures that the major components are in good condition but that they have enough life remaining to engage insurance coverage.There are a lot of ways to make an offer more enticing without boxing your client in.

He has a YouTube channel too and gives lots of good info on promoting your STR, dealing with the ABB algorithm, etc. 

Indian Rocks Beach openly promotes it and it is completely legal - no hotels there.

Even consider investing in a professional website, building an email list of potential buyers, and using social media to promote your deals.

They are set up to promote home ownership not businesses.

You, as the investor, are responsible for getting as creative as possible to entice the local talent to want to be part or your 'Rockstar Team' and to bring you all the best deals. 

Versus having an HVAC system where it looks cleaner and might be more enticing to tenants.Thoughts?