My guess is that a lot of these sellers will either exit their current loan or be open to subto as soon as the rates ease up. 

Here's my list on top of the obvious request for all current lease agreements.  

We had to sell but were told in its current state it was only work 600k.

I'm looking for an investment strategy that should make at least a ~10% CAGR on my equity (to compensate me for the extra effort of not sticking to my current low-maintenance investment strategy), and that would allow me to invest at least $100k per year.

I currently live in Michigan, but I plan on moving to Florida.

If the accounts are in individual names, then the person whose name is on the account will need to be on the loan.Although you mentioned that both of you have the same credit score and history, consider who currently has more financial leverage or could benefit from additional credit activity.

We negotiated it down due to current condition and the fact that the owner was out of the country and needed a quick sell.

In its current state I would be unconcerned.  

Currently I am just researching to find out if this something I would like to pursue.

Where do you live currently?