After the conquest of Constantinople by the Ottomans the population of the city was found grossly lowered. Many buildings were already deserted before the time of conquest. Mehmed II immediately started construction activities to build a new Turko-Islamic capital. During his reign there was no ideological systematic conversion of churches into mosques, the Byzantine building stock was used for the new functions necessary to be fulfilled urgently. A new group of elites was formed among soldiers who got richer by spoils of war and some buildings were assigned to them to form the new neighborhoods. Needing people for constructions Mehmed II took some extra ordinary measures to raise the population including allowing the escaped locals of Constantinople to reoccupy the buildings they left without paying taxes. He also called for Ottoman elites from former capitals; Bursa and Edirne offering them priviliges such as occupying any empty palace in Constantinople without payments. This paper deals with the function change and ownership of Byzantine building stock after the Ottoman conquest.