@Jake HughesCost segs can be an amazing tax deferral mechanism but they are not a one size fits all solution.  

If you can’t quantify risk and don’t understand the mechanics of “weighted” average of expected return and range of returns (standard deviation) then you are at a severe disadvantage and should consider a competent investment / financial manager for your investment capital.  

In your property folder I'd include a "Closing Folder" with your closing statement and original home inspection (all your major mechanical pictures and ages are there).

Why are you re-installing mechanicals on vacant properties - after they've been stolen?

Depends on the age of the building, mechanical systems, etc but good rule of thumb is 6 months of reserves liquid to feel safe

You have a mechanical skillset you are perfecting so you will always have your trade to barter for access.

Basements (if they have them), roof, attic, crawlspace, exterior, and all mechanicals are where all the unseen costs are not in the kitchen, bathroom, etc.

Are there separate mechanicals for each unit?

Are the separate mechanicals for each unit? 

@Fahima Hilal an architect usually only outlines mechanicals, plumbing & electrical on their blueprints.Your contracts should be creating appropriate drawings showing where their stuff would go and submit to city with their permit application.