I had it a while back and didn't like it, wondering if upgrades have been made. 

Kitchen and baths were vinyl, upgraded at sometime in the last few decades. 

Say you want to do $5,000 in upgrades...I would certainly not run out and get brand new cabinets as a first option.

How do you walk into a house and figure that upgrading a certain part of it will return you greater value than the cost?

My question is about timing of the upgrades. 

I sent new landlord letters to all of them informing them of the change in management and advised them how to pay rent, when rent was due, who to contact for maintenance issues, and upgrades we planned to carryout on the property.

I just smile and say "this unit doesn't have that" or "I might consider some tenant desired upgrades after a few years of positive occupancy." 

I’m a GC and electrician by trade so I’m planning on staying in one unit, completely upgrading it and move on to the next units.

We are following the plan to upgrade and improve it.Lessons learned?

Cosmetic upgrades