The UK Land Registry publishes open data on real estate transactions on gov.uk. The datasets are publsihed in txt and csv formats but their size can make them difficult to work with.
So I've got the huge .csv file -> pp-complete.csv
You may download it here. Done? Now you see that each line contains an information about property in the following form:
{F887F88E-7D15-4415-804E-52EAC2F10958},"70000","1995-07-07 00:00","MK15 9HP","D","N","F","31","","ALDRICH DRIVE","WILLEN","MILTON KEYNES","MILTON KEYNES","MILTON KEYNES","A","A"
Here is an explanations of column headers.
The purpose is to find all properties that has been sold two or more times, and write the result to a separate file.