These zipcodes offer really high rental yields even accounting for the vacancy stats.

@William Hochstedler  tax sales generally are run by state law.. and then the counties follow those rules or laws. not sure if each county sets a separate agenda or rules or laws.your correct though a simple call to a title company and get the head title examiner on the phone if you can... you would simply say I bought a tax sale property and recorded my tax deed how do I get title insurance and if there are any liens or encumbrances other than ad valorum tax's or IRS liens do they get extinguished that's what you want to know.Also are the sales on line like they are now in many CA counties  Bid for Assets handles most of CA.

I've had no pet damage.I'm seriously happy for you, but due to stats, you're probably running on fumes.... :-)It's easy to spend >$15k rehabbing really bad pet damage.But you have a good point, it's just a roll of the dice IMO....

Beyond what I listed above (population projections, tenant demographics, crime, main movers in local economies, environmental risks, etc all stratified by city/neighborhood), do you recommend any other Real Estate adjacent stats to include in my research?

Don't buy there if you don't like the risk/reward stats of buying in such areas.

So you want to make sure you expand your portfolio at a sustainable rate so that you are always comfortable from a cash-flow standpoint.You may also wish to share your numbers here for your current rentals so that we can examine it more closely and give you better feedback.

Multi family in particular the stats are amazing.

You need to examine your competition.

Here are the stats so far:149 Total Calls1 property under contract, with 2 more to be completed soon.

They're stats, straight from the MLS.