The most secure jobs are skilled direct income producers (think of mechanics, nurses, teachers, experienced casino dealers, etc.).

New to Mid life mechanicals in place (Water heater, electric panels, furnaces), no foundation issues (with a condition of accepting damp basements, nature of the typical stack stone foundation popular in the area), no major exterior defects (didn't want to deal with roofing going into winter), rent ready (legally had to accept tenants in place of course).

Roofs, mechanicals (you mentioned AC), unit condition/age/style, appliances, etc.Additionally, what is the neighborhood like. 

For example let’s say a property COULD be worth $200k if it was all fixed up with brand new mechanicals and cosmetics.

Being an investor-friendly agent vs wholesaler require different skillsets, although the fundamentals are similar but the mechanics for doing deals will be different.I think the best move for you would be to join a brokerage that is investor-friendly & also offers training in wholesaling or is at least friendly toward it.

If all three of the units are equivalent then 2/3rds of that capital gain would be from investment and 1/3rd from primary residence.The mechanism is that when you sell you will start a 1031 exchange and take boot in the amount equal to the gain attributed to the primary residence portion up to the maximum allowance of $250K ($500K if married).  

You cannot guarantee that the property will appreciate, and if value stays the same, everything is going to be old in 10 years and you'll start to have to spend money to update and replace mechanicals.

One next door neighbor runs a mechanic shop out of his property, the other is vacant and hasn’t been lived in or mowed in at least 5 years.

The mechanics of a personal vs business savings account will be nearly identical meaning they work the same and the interest will be roughly the same. 

And, we are planning on making some significant changes to the mechanicals of the buildings.