You should have determined the property lines prior to purchase. 

This is a terrible way to determine who you should rent to. 

Depending on price and size of the building will also determine amount but I would guess start with $5-10k at the beginning and as it cash flows add money to the account till you reach 10% of the value of the building.3.

Are you trying to determine something specific?

Combing through the tax assessment files, finding the chain of ownership, determining what municipal liens might be attached and scouring Statutes relating to tax foreclosure laws in my state/county (did I mention that I am quite adept at research).

If it is then go ahead and determine if this is something you actually want to do. 

I used this rental property calculator with very very conservative numbers to determine if this might be worth it, which it seems to be.

Be a Betelgeuse...There are elements of their household that seem determined to stay no matter what. 

As always, your price will determine where you can look.

I'd say analyze the market you are looking to invest in, and determine how has that market responded to the pandemic?