With that said I just recently had about 12K of capex on a duplex unexpectedly the first year we owned it. 

I’m unsure if the duty owed is my A/C will never unexpectedly break down.

I think bp should have a dedicated fail section, as the best lessons are the unexpected kind!

In my experience, when residents have unexpectedly high heating bills, they gripe about it, their ability to pay rent is reduced(leading to a higher eviction rate,) and they tend to leave the apartment at the end of their lease, dramatically increasing turnover.

What I call "an emergency" is something along the lines of a family member/close friend who was just in a serious auto accident and is undergoing life saving surgery.

I would say I  already completed a deal but it was more of a happy accident, I purchased my condo as a short sale several years ago and as of last year it is appraised at triple what I paid for it.

Just keep building your business, do deals, and you run into the good ones by accident. 

Secondly, many condo associations are run poorly and have little in the way of financial reserves, so unexpected repairs, maintenance, or upgrades could translate into surprise special assessments that will gobble up your profits.Flipping off-market properties is a sound strategy, but it requires serious marketing effort.

Things break, accidents happen regardless if it's 10 days or 10 months into a rental.

The 401k protection you mentioned applies if you were in a car accident, for example, and someone wanted to pursue your assets.