I noticed that there is a divot in the roof that I asked about last week, and now I noticed that there is a crack on the brick siding of the house.

You probably want to insure for replacement cost rather than what the insurance company determines is the depreciated value of your home or a component, such as a roof.

I knew going in that it needed extensive repairs including new roof and foundation work and probably a rewire.

If it does not, the chances that you have a significant problem are minimal.Your first remediation is to go outside to look for a slope leading toward a basement, or roof downspouts emptying very near a wall.

There you'll find a network of buyers under one roof, for 3 hrs.

Very little cosmetic work needs to be done, the kitchens are updated, the floors are done, there is even new wiring, plumbing, roof, and windows. 

Painting, carpentry, flooring, installing and repairing appliances, running gas/water/electric lines, roofing, etc I and my wife do myself. 

It's not habitable and needs money to replace the roof, install furnace, and other things before the cold air moves in.

I scoffed at them as I loaded plywood on the roof with my crew, working side-by-side with my bags on.

In fact, let me preface with a quick list of pro's and cons for a multi-family as compared to a single family.Pros:Proportionally lower taxes/insuranceEase of management(locationwise)Lower roof capital expendituresHigher rent to price ratioRarely fully vacant - can reno-rotate tooLow price volatilityCons:May pay minimum management fees due to lower unit rentsGreater potential for delinquency/damage(Much) higher HVAC capital expendituresLow price appreciationOverall, it's a somewhat bizarre phenomenon to me to watch the money rushing into multis.