In this instance however I know the Seller (RE agent who I have bought from before) and the RE buyer agent for us (who I have bought through before). 

For instance if I was buying a single family house 2bed 2bath, could I say she was going to be renting one room and will be paying X amount.

Short answer is as little as possible.The long answer is it depends on the deal.Typically you end up in a subject 2 situation when the current owner has little or no equity in the property, the current advantage of subject 2 properties is that most mortgages are below current market rates.Keep in mind when acquiring a property subject 2, in most instances you are not notifying the current lender of the change in ownership, and most if not all mortgages have a due on sale clause, which is the lender's decision if they want to enforce it or not.I personally like the idea its a great way to get investment properties with low rate loans, that with most likely appreciate in the coming years.

I have transacted at least 5000 properties as a flipper developer and lender and I have had one instance of this. were someone recorded a mortgage 5 minutes before my loan went on record so when I got my title policy I was in second instead of first made a claim to my title insurer and they rectified it quickly and went after the bad guy criminally. 

In these instances, you'd have to check things like flooring, plumbing for leaks, roof for leaks, hot water heater, and heating and air conditioning units. 

It seems like towns could dictate if you can build an attached vs detached adu for instance. 

For instance I was seeing insane growth and development in pasco county, wesley chapel areas outside of tampa, and actually had a hell of a time finding industrial space in Bradenton FL, so at least on the commercial side of things from my limited experience there didn't seem to be a down turn or softening, so its so interesting to here your take on your local market there as well.  

So for instance for our lead organization & management, I clean the lists up in google sheets and then download as a .CSV file and upload into Airtable (google sheets on steroids) where its easier and cleaner to manage.I use Airtable to manage our raw leads data - I have a trigger set up, that whenever we change the status to "qualified", that lead will go into our CRM (Salesmate.io) where we track our contacts and deals.

I've heard of instances where I've seen the investor do well long-term and some where the investor has been able to build and sell or just hold and eventually sell if new developments are coming up in the surrounding area. 

In your instance of being an OOS landlord I’d look at placing a property manager until you can non-renew her.