Are you currently working on lining up funding or looking at potential properties yet? 

Have proof on hand (easy enough to find) online of the missed tax payments and any documentation that supports that he specifically didn't pay his taxes.Probably a simply mistake on his part, but now if he wants to develop on it, he either has to land lease it from you or buy it back.I'm not sure how the whole tax deed thing works, so that would be something you have to figure out between the two of you.

If you've got to ask a question on an online forum about managing an out of state or out of country renovation, you aren't ready to do this on your own.

If you don't get access to the property before closing it can be tricky but if there are recent photos online or you can walk through before and take your own then it is much easier.

I offer an online payment portal to submit rent payments via ACH or CC - they "couldn't figure out how to use it" so I set us up to accept Zelle payments.

I’m not a betting man.

I know this is a differing topic on the forums, and online in general, but having the legal background/education and knowing estate planning concepts you'll realize it shouldn't be.  

In both my seller financed deals the primary bank I was betting on backed out.

I suggest finding an online bank that gives high interest rates.

I have never heard of this metric and don't see any information on it online.