But that shouldn't really affect your ultimate returns in any meaningful manner even if you use IRR method.  

Look at is probability of sustaining a loss that exceeds the levels of coverage.  

Fortunately, I have a natural tendency to do the right thing and in a timely manner so his complaints to have "safety" issues addressed are not too much of an inconvenience for me (although the renter himself is an annoyance). 

With that being said, I think there is plenty of work here to atleast sustain a strong rental market long term.

Percentages vary depending on your strategy but here is generally how I use my excess cash from this portfolio: Say you have extra 1,000 bucks after paying your monthly expenses and putting aside money for reserves: I split it out in the following manner. 1) Additional rainy day fund for CAPEX and repairs. 10% 2) Additional Acquisitions budget 50% 3) Additional Debt paydown 25% 4) Stocks / Bonds/ Pay myself. 15% I definitely prescribe to the pay myself first , and have a more conservative approach when dealing with debt .

This has proven ineffective as most of these properties' income can barely sustain themselves [even with a "larger" (20%-30%) amount of equity down] and the ones that do have worse returns and higher risk than if you were to put money into a CD, for example. 

My biggest issue currently is I have worked with some higher net worth individuals to partner on deals in the past, structure would be they provide all money and I do all of the work and we split profits in some manner.

I know many unable to sustain heat with heat pump only in the north.

Prices went up so high so fast, I don't think "sustainability" is in the vocabulary for King, Snohomish & Pierce counties. 

Especially if you are financing as the holding costs may eat up all of the profits in the event the contractor doesn't do their job in a timely manner.