The deed fee is 4% of the declared value, legally 2% from each side and in practice usually carried by the buyer. Declaring below the real price to shave it is tax fraud, and it caps the cost base you will one day be taxed against on sale.
Building code year is the first question in this city, not the last. Ask where the building sits against the 1999, 2007 and 2018 revisions, whether it has been through kentsel dönüşüm, and what its DASK policy actually covers. DASK is a legal minimum, not full cover.
Some parcels still require military-zone clearance before a foreigner can complete, and each district has a foreign-ownership quota that can block a transfer outright. Both are checks to run before money moves, not after.