They no longer sell components for these systems and, if they fail, it's basically "start over".  

This may not be very expensive if you will do multiple flips in this entity as you can then leverage the low cost day labor for garbage pick up/hauling, etc.2)  Temp agency that has work comp on the workers3)  Hire a contractor like a landscaper who will have work comp and lower end labor costs4) Get a bottle of Advil and start doing it yourself

I am talking to a land owner about putting a letter of intent on a land in an urban locale and get it approved for an apartment complex of around 50-60 units, with 30% affordable component to it.

Other than the outer walls, there are other components that has a shelf life: roofs, boilers, chillers, ACs, plumbing, etc.All of these will have to be replaced over the years but once you do you it will serve you to years to come. 

There is a lot of variation in this depending on the building type, age of the components, class of building, demographic, amenities, etc.

A major oversight or really lack of insight is the missing market analysis component.

What I have learned through their wisdom is that retail needs 3 components to be successful.  

If the loan won't be sold to Freddie/Fannie, I don't believe the AMC component is part of the equation.

It is missing key components represented to the buyer as being present.

And if there is immediate deferred maintenance, you would need to subtract that off your offering price (or at least half of it, since you'll have new components).