This place needed a lot of work initially - new windows, roof, mechanicals for starters.

If there is a mechanical failure in the unit, then it may be able to keep the home comfortable, without the occupant even knowing anything is wrong. - If a system is low on Freon it will run longer, taking more time to heat or cool, and increase the utility bill. - If there are electric heat strips, then there could be a failure causing the electric heat to run when it isn't supposed to or that causes the electric heat to run, because the primary heat source is not functioning properly. - If there is an airflow issue in the home (collapsed duct work / dirty filter) it can cause the mechanical systems of the home to provide inefficient comfort (longer run times) while working harder to achieve comfort (higher amp draw). 

You also do not want a "popup" mechanics garage...etc.

What are the mechanicals of the building,  Is the electric sound, plumbing, sewer lines, general layout, can we improve the units without moving walls, structure changes, etc that make sense.

An example from my bank's 10-K (bold emphasis is mine):Deposits are the primary source of funds for our portfolio loans, loan pipeline and investments.

.), unpaid taxes, and mechanics liens, to name just a few.

It's all about supply and demand/buyer pools mechanism.

“DEFECT” DEFINED: For the purposes of this contingency, a defect is defined as a structural, mechanical or other conditionthat would have a significant adverse effect on the value of the Property; that would significantly impair the health or safety of futureoccupants of the Poperty; or that if not repaired, removed or replaced would significantly shorten or have a significant adverseeffect on the expected normal life of the Property.

I work as a mechanical engineer but have become extremely interested REI over the past 6 months.  

Understand the differences between an operating expense (normal and recurring) and capital expenses which are infrequent, larger expenses for things like roof & mechanical replacements and value add projects such as painting and other remodeling.I recommend talking to a CPA to get professional advice.