Historically there have been more than one encryption schemes advertised as "non hackable" only to later be hacked.

Years ago I got a tax credit for doing rehabilitation on a building that was listed on the National Registry of Historic Places.

That's historically low not only for that product, but in general.If you currently live in a single family property and try to buy a mutli family property, most underwriters wouldn't believe that you're actually going to live in the property because like you said in your post, the current house is not big enough for a growing family. 

I just bought a house in historic downtown Hattiesburg!

You can see it historically even on the biggest collapse on the market in 2008, where real estate bounced right back after a few years, and it's more expensive now than it was at the peak in 2006.

Currently the government is pumping historically unprecedented amounts of cash into the economy, we have a global pandemic (round 2) on our hands, and telework is changing the way people think about living and working in one place. 

In the area where I am specifically looking (Chester County), I've been looking at the historical data for renter-occupied vs owner-occupied and the numbers have slowly risen - to me this is a good sign of an area I believe I should be looking for as I start this journey.

I do not know the metrics for the area, but if the population is growing, jobs are diverse, historically RE appreciates faster than CPI, you indicated nice area, this may qualify as a single.  

I’m in San Diego, housing price is historically high, I was so attempted to move the investment  to a better school district, but of course property tax and everything else will be more expensive too ..  

If you are using appraisal with plan for commercial use they may be able to factor historical information, but I would doubt they'd have the experience or speculation to factor what potential short term rental income could be.