-If the previous 18 months are any indication, my guess is borrower does not have the means to make any progress on current overdue balance, and will add $6,000-$7,000 each year to the overdue balance (Tax payment of $5,500 and one or two missed monthly payments).

His recent posts indicate that the online tax lien sales have become so competitive that they are no longer a very good option for individual investors.Another site that I have used is taxlienlady.com She has a paid subscription that gives you access to more info and monthly webinars.

Zillow's own data (you can find it yourself if you search their site deeply enough) often indicates that their Zestimates are often 20% or more off-target for a given county.

Zillow's own data disclosures indicate that the are often 20% or more off target.The "MLS values" are the actual asking price or "sold" price for a property.

Below are some questions I would think would be a good starting point for you to see who really treats their company like a business or a hobby and it will give you a good indication of how they are running their business...

It gives the seller confidence that you have the ability to purchase the property without having to jump through hoops to get a loan or otherwise figure out how to acquire the cash to make the purchase.A proof of funds is often just a letter from your bank or even just a print out of a bank statement indicating you have the money to make the purchase.

Lack of response from anyone else seems to indicate (to me, at least) that others understand. 

If you take on too much risk for your comfort level, then you're not going to have a happy life and you only get one life to be happy.On the duplex, you indicated the list price is $40k and that it's been sitting for 6 months.

Give them a general idea of what you after (ie a mortgage on a 40K house, but some friends have indicated a loan that small might not be feasible) and ask for his guidance.

I've found their answers to these questions to be a great indicator of motivation and as a consequence, an indicator of the potential for a deal.