Kitchen design, or general interior design?  

I spend 3-4 hours per inspection and when I finally get to the interior it becomes a breeze, I've already identified area that need further investigation, and can look harder at those areas, but twisting a knob, closing a door, opening a window, etc takes seconds.  

This new one has close to 10 interior doors.

Me reading your story is like watching a Rocky movie...you've never stepped into the ring but after watching it you feel like anything is possible.Did you have someone come in and design the interior or did you do everything yourself....and did you stage the home in order to sell it?

Age of roof, age of HVAC, are the tenants actually paying the rent, overall condition of the interior, Etc If I were you I would start working with an agent who can guide you through this.

One of them has been substantially redone while the other three are mid to strong exteriors and gutted or needs gutted interior.  

I'm an Interior Designer by Trade, with my own business.

I have been searching all over the internet for some ideas of what to do with it (as reasonably as possible) and while I am finding tons of info on interior rehabs, I just can't find too much for the outside. 

The potential downside is that if the landlord is walking away he or she may have quit collecting rent, so you may have a tenant who has become used to living for free.I have never had a potential tenant in this situation ever not let me walk the interior of the property.  

I specialize in kitchens, baths and interior finishes.