@Ben Miculob  It looks like you have two different types of comps here.  

They would almost be guaranteed to lose money if the owner could not pay...The two types of sellers who are most open to Seller Financing in our experience are:- Sellers who are stuck on their sales price.   

Well, I'm not advising that someone is definitely up to no good, but if they haven't provided you with any type of comfort, peace of mind, and trust that you need just shop around as much as you can.  

What type of units are they?

I have a shop in my town that has all sorts of legal documents for $5-$10 per.2) Option agreement - You can find these also at the same type of shopThese two documents MUST be separate documents.

I think just buying a retail type property might get you the equity growth from just the overall market appreciating, which is not always a sure thing. 

I’m assuming they make some type of commission off of the estate sale?

Once you see their photos you'll get a solid glimpse into what type of lifestyle they live aka how they'll treat your rental. 

They are not the same thing, but if the building was constructed prior to 1969 without undergoing a change in occupancy type and no major renovation permits pulled, it will likely not have or require a CO.

It very much depends on the person (you), area of the country, type of property, partnership and what type of work needs to be done to get property rented or sold.