The seller purchased the property to do a favor for someone and the person died.

Assuming you have access to MLS (Multiple Listing Service, a place for agents to list deals).1) Look for deals that look like investor-type of deals (e.g. low purchase price, ugly houses, or sometimes MLS will even say what type of financing it is)2) If the buyer's info is there, voila.  3) Otherwise, contact the realtor to look for leads (that will be more of a uphill battle, but you never know...)

I’ve isolated these three markets as they’re all within driving distance from my home and seem to fit my budget of $100K-$200K for purchase price.

You could also purchase below market value. 

Is it possible to purchase the unpaid taxes as a lien investment that will permit foreclosure within a specified time frame?

My current purchase (closing in February) is a luxury cabin that will be an STR.  

@Kristian Forbes Short of doing another house hack or negotiating the purchase price down a fair amount, I think that's going to be a tough one to make the numbers work.

You're gonna want to be around $400k purchase price to be in a good area too.

The people who struggle here usually underestimate those factors.One thing I do differently than most: I share actual performance data from my rentals—purchase prices, rehab details, rent numbers, lessons learned, and backstories.

If you purchased on Monday, I am assuming it was an upset tax sale.