It is like taking your car to a bad mechanic.

How about a mechanic? 

I know about necessary egresses and about quick release mechanisms for window bars and about alarms vs. window bars... 

The difference between YM and STD DEF have to do with the mechanics of swapping out the promised interest.

Inspect ALL the units and get a professional property inspector to give you an assessment of the mechanical and structural components to determine your renovation costs accurately2.

You may wish to confirm that the new 401k provider has experience with the particular investments in which you intend to invest your retirement funds as you very likely will have questions in terms of the mechanics (e.g. how do you invest in real estate, etc.).3.

They might be able to control their usage to avoid a rent increase next year.Possibly think about: increasing attic insulation, putting utilities in tenants' name, requiring that all light bulbs are LED, and getting energy efficient mechanicals/appliances if they're not Energy Star already.

The mechanicals were in good condition to begin with all being less than 10 years old.

I am just starting the difficult path of becoming a Mechanical Engineer.

A great many more forum posts about people looking for guidance on the specific mechanics.