Dan your market/assets/tenants are on a totally different level than a good majority of the rest of the country. 

Total build cost?

In my opinion, more important metrics are total profit and time spent managing the operation.All marketing works.

Now I am totally confused!  

I totally understand that it depends but I think what I am looking for is a bit more input and guidance.

The current owner listed last years income as $51,000, but currently has rents at (for the five separate units): $650, $750, $800, $825, $1125 (the math doesn't totally add up so maybe he changed a rent payment at some point). 

It is very embarrassing to admit that a woman who has been an entrepreneur, taught college, and accomplished a few things in life, could be so totally taken in.

I resided in the home until summer 2020 (total 2 yrs 9 months) and then deployed overseas for the next 4 years; selling the home in June 2024.  

Totally agree with @Mitch Davidson.

I usually hold 15% total for these.