The accuracy is more dependant on the type of property and has nothing, or very little, to do with the value.A SFH will generally, over the life time of the property cost 50% of the rental income to maintain the property.

Actual human inspections will produce more accuracy.

In fact, I have a question about the accuracy of this book (see the end of this post).  

Account Closed, if there was a model based on data to predict bubbles with great accuracy, we will all know when to pull out or not get in.

Given the track record with the accuracy and thoroughness of listing data, I won't be holding my breath on timely updates of sales data.

qclemons,The other issue here is accuracy.

How you you guys do this with accuracy prior to putting it under contract?

For more accuracy, just take a deep breath, grab a large coffee and line by line an excel spreadsheet.

Please keep us posted as to the accuracy those theoretical numbers, vs reality. 

For the tax break we would lose some control and at the time the most issue for people was window replacement and historical accuracy.