A gross yield figure on its own is close to meaningless. A proper net-yield model states its assumptions for vacancy, management fees, maintenance reserve and annual service charges separately, so you can see exactly where the return comes from and stress-test it.
As a rule of thumb, well-let apartments in established rental districts such as Kadıköy and Şişli return a net yield in the 4–6% range once realistic vacancy and management costs are deducted — anything significantly higher on paper usually hides an optimistic vacancy assumption or ignores service charges.
Before committing, ask for an exit scenario at years three, five and ten, not just the entry numbers. A property that only works on a best-case sale price in year one is not an investment case, it is a bet.