I see one aspect missing. 

I'm a fellow San Diego resident who is also interested in multi-units OOS.In response to your question, from the research I've been doing (and outside of the residential vs commercial aspect that @Sherwin Gonzales brought up), a big part will be your comfort level and financial goals. 

How will Millennials and Gen Z prioritize aspects of living and define quality of life?

I want to learn every aspect in the investing.

I am 23 from Cincinnati, Ohio and currently working in Commercial Real Estate, really enjoying every aspect of it and learning a lot.

The reason is so you are educated on the legal and ethical aspects of selling homes. 

From the podcasts to the blogs to the articles and the forums, there is in-depth information on every aspect of real estate investing.Also, since you're coming back in the game, consider going to a local real estate investment club to network with other real estate investors and professionals. 

You are spot on with the planning aspect for sure.

@Ian I LeinwandFrom a Private Money Portfolio lending aspect you would most likely have (2) options on a (2-4 unit). 1) Rehab/Fix and flip type loan if rehab/repairs are needed >$5k- Depending on experience and Credit, acquisition LTV would be between 85%-95%, estimated Interest Only rate 7.09%--9.99% w/ 1 point for 9 months.  2) Rental Loan (2-4 unit), Depending on Credit, Max 75% LTV (80-85% SFR), Estimated 5/1 ARM rate 7.125% Full AM. or 7.375% Interest Only w/1 point.  

However, my most of my questions are in the funding aspect.