I have purchased several deals where the house was just a shell and had to rehab everything from plumbing to electrical to roof , etc. it's a massive headache and extremely time consuming.

A lot of new drywall, plumbing, electrical, sub floors were added/replaced to kitchen, new windows, siding/gutters/fascia/soffits, flooring (much of home had original hardwood), plus all the visuals you see on photos (cabinets, granite, trim, etc).

Although I can't really offer any advice on the  analysis side of things, I may be able to help if you are in need of any plumbing, hvac, or electric work with any current or future properties you invest in. 

As a contractor I always prefer a full gut but it does eat away the rehab cost and takes longer but no stress about plumbing, leaks, electric, lead paint and etc in the future.The patch up would cost less, fast timing, but then you are gambling with what's behind the wall and hoping nothing happens in the future.I assume most house that are purchase for BRRRR purpose are in distress/bad condition and old on some occasion.What rehab number would you go for?

After the inspection it comes out that despite the structure being sound, HVAC electrical plumbing and roof are pretty old and may need attention soon.

The oven has an electric igniter that has to remain on while the oven is on.

Now when we look at the surface items (flooring, kitchens, paint, lawn care, etc that is pretty easy to replace but that tenants habitually destroy) vs the items that really matter and can suck up a lot of funds (electrical, bathroom, landscaping, etc.).  

I have been researching to see how much it would cost to rehab the house but I am sure the roof, electrical and panels will need to be redone.

If you wanted to fight one mortgage for both units, look at the electric meter and water meter for the building.

3 apartments - probably a C+ to B- building in a C location:#1 2BR Rents for $600 currently#2 1BR Rents for $480#3 Efficiency rents for $500.Apartments 2 & 3 are on the same electrical, so their electric is included.