This is one of those cases where ancient religious law collides with modern day facts of life ,and as a result religious law makers find elaborate loopholes to bridge the contradiction.

This article is written from a Canadian perspective but still desceibes the methodology well, recommend you check it out.

The IRS' preferred methodology is engineering-based which costs more.

Zillow even publishes their accuracy rates on a county by county basis, and they are transparent enough about their methodology that anyone who bothers to look at how they come up with an estimate would realize that it's worthless.  

I am italian living in Rome and working in Abruzzi.You have a lot of Ghost ancient Towns.Usually the city requires you to sign a committment of rebuild before selling to 1€.Typically Is a small Town strategy for keeping alive.

The approach I use now is actually very different from the one that Jack lays out in his course (I don't use a lot of his exact methodology anymore), but he did play a major role in making me aware of the niche in the first place, and it helped me to identify what does and doesn't work well with my own personal style.Anyway - all this to say, Jack's approach is legit.

I've been using that methodology and it has been effective.

In the very ancient world, folks can just create website from geocities dot com, before they able to create an HTML page.

So our goal is to acquire the home/office addresses for owners of facilities in order to insure they see our mailers.My methodology so far has been to go county by county, identify all self storage facilities on Google Maps (double-checking with our database to make sure I don't miss any not on Google,) and entering the addresses into a tax parcel GIS unique to the county.

Do you have a methodology to determine basis?