I was required to add exit signs in the shared hallways / stairs, and to add interconnected heat detectors in all units, and to upgrade all smokes in all units to be hardwired, and to create 1-hour fire separations between the three units, which we accomplished by painting the ceilings and walls shared with stairwells/common halls with intumescent paint.

Cosmetic Light Renovation, brightened it up with white paint, refinished the floors and stained coco, light carpentry, exterior fascia, treads on the stairs, and brand new SS appliances in the kitchen.

So, I will re-side, new roof, new front stairs, new windows, a couple dormers(to your point), build out a basement bonus room, and gut and rebuild the other unit all for under 300K?  

A leak under a cabinet is not so bad to deal with, even if there is some wood rot, but the pipes going to that interior bathroom or upstairs bathroom or the pipe through a cement foundation can get pricy to fix. 

Maybe a second home could have interior and exterior stairs, plus an ADU.  

They all have a hatch which is one egress, but in order to get the other egress we would need to build out of a cement foundation which would be expensive.

@Gaurav MehtaFoundation cost around 5k material labor  Excavation forms cement Framing Cost around 6k labor material. 

In general small repairs that don't modify the design can be made to a deck without a permit but if you add or remove anything, or the deck is a certain distance off the ground (30" in my area), or the repair involves anything structural, the handrail, stairs, stair stringers, etc. then you need a permit.

The interior to the house is completely tarnished, so cabinets, walls, ceilings, stairs, flooring, paint, appliances, etc. are all trashed.

To me, this just cements the idea of buying value-add in solid B class neighborhoods in cities with strong growth numbers and economic drivers.