It will equally blow your mind.  

After that, assuming the furnaces didn't blow out and cost an additional 4-6k to install and replace each, I would not reach a cash on cash return of 100% until year 5, assuming everything held together fine and there were no major repairs.

Downside: They cost moneyIf you get a bad one you end up doing a bunch of work that you shouldn't be.If you don't educate them up front, they may spend money on things without asking you first per the management agreement.There are times they advocate for the tenant more than the ownerFinding a good one:  Read google reviews, ask for referrals from other landlords, check the BBB to see if they have many complaints, ask in bigger pockets

If you have not read SOLD yet by David Greene, its worth it and honestly its better than anything Garry Keller has written on the topic of being an agent, and his books in my mind were the industry benchmark for agents prior to Davids book coming along and blowing all the competition out of the water.  

You can't just point to the times you blew on the dice and got snake eyes as proof that blowing the dice causes snake eyes, you have to look at all the incidences of blowing on the dice. 

Welcome @Justin Lacsamana and thanks for sharing your story.I'm a huge fan and advocate of House Hacking in especially in San Diego especially taking the route of residential multifamily (2-4 units). 

I’m trying to wrap my head around the macroeconomics of it all and would appreciate others opinions and also any devils advocates.

Many many lazy agents out there that blow my mind little effort they put into a deal.

I just tell them I represent the owner so I can blow off the sob stories easier . 

that is a huge blow back to women. coming from another woman.