Budget time and energy to manage the property manager. 

But by then my wife became a stay-at-home mom and my DTI prevented me from getting larger mortgages. 

If you are targeting small multifamily properties, that statement can be true, but if you are targeting larger units, the chances of paying cash are very small to none, as many people will buy it using banks and a mix of syndication, so savvy investors will ignore your letterThe PS section where says " or if they have tenants in the property."

Give it a year more or so and that rental income will go up and with lower rates, the numbers will make sense for him if he refi's.And for the larger properties

You can run multiple small deals at once, or run 1-2 larger deals at the same time.

.: Quote from @Susan Real: Really hate to speak negatively, as I don’t ever like to drop to that energy, but I must use my voice to steer women away from this.

As the deal size gets larger, this should get lower. 

I'd like to use these to upgrade into something much larger in the next 2-4 years. 20+ units.

Lastly, my initial goal is to house hack so I can theoretically live free for a few years, while buying multiple MFH to build a larger portfolio quickly.

What would be interesting to me if a software/program could do this analysis at a larger scale in order to identify off-market properties that have "below market" rents that would help prioritize someone's off-market focus.