He has a construction/flipping background, is very thorough without being alarmist, and makes a nice report with photos documenting his findings.  

How long have the tenants been there, and can the seller document the payment history?

Now that it would be a short sale, you'd have to get the auction postponed, which would take presenting some specific documentation to the judge at a hearing.  

What contracts and disclosure documents do you use for sub2 and lease option?

You would need to do a walk through as the old tenants move out and document the property condition...

I don't know how to access your specific county's online system, however this is what I suggest you do to get started:1) Unless involving a guardianship for a minor, probate cases of Decedent's estates are public information. 2) Ask to see the Registry of Actions or similarly title list of new cases3) Start with a single case, typically the most recent filing.4) Request to pull the actual file to review5) Review the folder and note the documents and the order in which they are inserted6) Don't even think of separating or removing documents. 7) Determine what data you need, including Decedent's name, case #, PR name and contact info, etc.8) Most researchers capture the data then scrub later.9) If this is too much work, either pay someone else, find a commercial list provider or work another niche.

Also, what kind of documentation should I have readily available considering this will be my first investment loan and I know there a stricter guidelines for these. 

It's natural for people to forget the exact conversation so make sure it is documented. 

Make sure you document all repairs, inspections, any other conversations that are important.  

They want to know if you can afford the place, even if the tenant doesn't pay, and if you have a history of paying your bills on time.