That means 8 roofs, 8 foundations, 8 interior units that need painting, 8 exteriors that need painting, 8 units that might need carpet/vinyl/tile, 8 hot water heaters or a single boiler, 8 AC or evaporative coolers (if there are coolers, have there been leaks?)

With a good renter, who takes care of the interior, it seems to me that this is a win/win for everyone involved.

So we need the assistance of an interior designer / kitchen designer / architect.

I'm assuming the interior walls need to be repainted anyway, so I'd paint the paneling the same color as the walls, as someone else said. 

Get with a good interior decorator..

There will also be good cash flow, and huge appreciation upside in this gentrifying area, once we fix up the interiors and rent to new tenants.

No matter the era of the home "Open" is the preferred interior look in my state.

At this point in my life, we are property tax payers, but I know that being in the military, where I go next, I will likely seek a cheaper apartment in a moderately safe area and seek a company that maintains their propertly well and addresses repairs and issues quickly, but won't care if the interior is dated looking so longs as it is clean and things work, but I am definitely not seeking a place with a yard that has to be maintained.

Maybe this is area-specific and your location is different, but I have found that you often have to write an offer on a multi unit property first, subject to interior inspection.  

They will dig around the perimeter  of the house in the affected area and sometimes into the slab on the interior of the house.