Would I expect appraisal district to capture the sale price as the new appraisal value (market price) in the following year and hence I ended up with significantly higher property tax?

Does the story make sense, and have you checked the local district court to verify if there's anything more?     

It was a quick drive by on my lunch one day and I stopped and wrote down some address of properties that appeared to be vacant.I have also been looking around the Old Oaks District.  

Over the past decade or so, as I have been able to move up to buy a larger house to support the growing family and then buy a house at the right school district, I continued to hold on to my older houses and renting them out.

COFI is the cost of funds index, also known as the 11th district.

I prefer SFH in decent school districts. 

So part of this is to get an attorney who regularly practices before the magistrate in that magisterial district where the property is located; that could help in determining what might be needed as proof.Let's see if we can get some attorneys to weigh in: @Chris K. and @Tom Gimer

My personal strategy is not to go after 3+ bedroom units, and I do not want to deal with multiple children, particularly in a poorly rated school district.

I would add that the strategy of bidding lower than total debt has been successfully challenged in many districts if the servicer goes after the borrower for a deficiency later.

She was calling to verify a tenant that wants to enroll their children  ( this house is in a very sought after school district ) .