Then you basically will another another entity to keep track of as either you register your existing LLC as a foreign entity in that State or you have to register a domestic entity in that State.

As with any new construction, you'll have a year of shakeout where you find things that aren't quite right -- a plumbing leak, a window seal, etc. 

New roof, furnaces, carpet, paint, appliances, mostly new plumbing, etc...What was the outcome?

That would be plumbing, hvac, electrical or structural.

For example the dozens of folks that have guaranteed they will lease my unit with cash in hand "tomorrow", the numerous contractors that have said they will arrive at X time for the emergency plumbing/heating/electrical work, or the tenants who say they'll have the money in by X.

I should not have high expenses considering all systems (HVAC, plumbing, electrica) are new.

Double check.Usually you want 7’ of headroom and 6’4” under plumbing and ducts in main walkways and the main part of the room.

The bigger items on my list include some plumbing, electrical, and replacing kitchen cabinets/sink. 

I'm not very experienced with flipping so I highly appreciate any good recommendationsHere are my first observations from what I see:2600sq ft duplex. 3+1 and 2+1Main floorNeeds paintMinor repair on floorNew kitchenPossibly new bathroomWater damage in one of the rooms ceiling and floor is in bad shapeSecond FloorPaintMinor floor repairNew kitchenPossibly new bathroomWater damage from one of the rooms, it is in bad shape.BasementCleanupPaintPossibly adding washer/dryerBackyardCleaning junkNew fence may beI've been told plumbing and electricity is working but need confirmation.

In another case, I bought a house with incomplete wiring, termite damage, and leaking plumbing.