Look very closely at the mechanical aspects of the building and obvious code compliance issues. 

What I didn't know in Philly is that when you pull a building permit, you must pull electric, plumbing, and mechanical with it.  

There are a few things to keep in mind from mechanics as well. 

Make sure you do due diligence such as check for tax liens, mechanic liens, law suits, drive by check for neighborhood status, location, location, location. also study the states foresclosure laws.

I am pretty sure with the proper tools and manual I could rebuild a transmission in my car, but the risk of making a mistake far outweighs the rewards, so use a professional mechanic, get a warranty and be secure knowing you made a good decision.My point is, we are not all trying to fly the jet, but do want to ride if its safe and makes sense.

It sounds like we are in much the same boat as I am a Mechanical Engineer be sure to check out the podcast as it is full of good info!

I also have full time HVAC/mechanical on staff as we do maintenance for our own and other property management companies.  

But I'm also wanting to understand the low level mechanics of all these types of transactions (will have 3 day class on lease option soon).For the #3 "OO sues" question I"m still a little confused.  

Most crucial things to look for are:Condition of the mechanical, electrical and plumbing systems.

In truth, I'm a mechanic that needed a building to work in.