And don't trust any pro forma statements they make, get the actual paperwork for rents received, operating expenses, etc.

I put them out day one and keep them out until they are rented or sold.I generally see an increase in traffic while it's up and I do receive phone calls looking for other properties, so it's working in some way. 

Sounds like maybe the lot sale was never recorded maybe, your grandfather is still listed as the owner, and the estate is receiving notice if the tax auction. 

Most agents receive in the neighborhood of 2.5%, so that'd be $5k in this deal. 

I've received dozens of calls and inquiries, but thus far they all have either had a very low income (rent would be over 50% of their net income) or they have a criminal background.

At that point do they want to be my buyers agent, making the offer and receiving the commission, or do they just want a finders fee if the deal goes through?

However the lease clearly states tenants must inform landlords and file an occupancy addendum or they receive a $100 fine.  

After I purchase the tax deed, I need to apply for a quiet title and after I receive the quiet title, I need to start the ejectment process.

But it was just a passing thought.Finally, we receive the closing date. 

Well...4 days later I receive an email saying "Congratulations!