Love the rental price feature... just wish it were a little easier to use.

1) it is an "estimate" based on modeling to list prices on Zillow; it is not a "price" and shouldn't be used as a price.

2) With the "mouse-over" on the Rent-Zestimate chart, it indicates the values and the date in the little box in the upper left corner of the chart.

3) The data can be downloaded if one has some proposed method for extrapolation; but most people that try to use such data for "predictions" have found their predictions not very helpful.

Web address for rent-Zestimate trend data:
http://www.zillow.com/ajax/homedetail/HomeValueChartData.htm?mt=9&zpid=#&format=json

Where # is replaced with the Zillow Property Identification number as indicated on the Home Details page, as well as used in the Home Details Page URL.

In order to import it to Excel as comma delimited, one would need to replace },{ with the "enter" character for each occurrence.  With notepad, you would do that by ctrl-F to search, },{ enter  to find the text.  Escape, then enter then F3, then repeat enter F3 until the end of the file.

Once in Excel you need to replace the modified millisecond UNIX time digits with a usable date format.  Do this by divide by 1000, divide by 3600, divide by 24, then add 12/31/1969 5:01 pm.  Adjust the time for the desired time zone.

(Actually, the last time I did it, I needed to add 1/1/1970 5:01 pm instead).