A. No, you need to have lived in it for during the year you sold it, plus in the 2 preceding years. Example: If you sell it in January 2016, you need to have lived in it yourself at the very least on 31. December 2014 (that takes care of 2014), all of 2015 and all the days in 2016 until you sell it. B. Apart from the fact that you cannot deduct the Grunderwerbsteuer (= tax when buying a flat/house) and therefore would pay income tax on 16,500€, correct. By the way, most Bundesländer have raised the Grunderwerbsteuer to 5% and more.