Average Housing Costs
Of course, your largest cost is going to be housing. This price will depend largely on the popularity of the area you choose. The numbers listed below, for example, represent the entire city's real estate as an average - including even some of the apartments in the suburbs which haven't been renovated for decades.
Central Athens and central Thessaloniki will likely be more expensive as they are the most coveted areas.
Athens
Based on a summarized report by Spitogatos, a leading property listings site with over 400,000 listings in Greece, the average price of sale for an apartment is 3,613 €/m2 (with 2 bedrooms) and 3,614 €/m2 (with 3 bedrooms). Rent costs are 12.4 €/m2 and 11.0 €/m2 for the same categories.
Note that the historic center of Athens is the most popular area in the city because of its close proximity to the Parthenon and other sights, and will likely be more expensive than the average.
Thessaloniki
The 2nd-largest city in Greece is known for its spiritual sights, churches, and Aristotle University. It is considerably cheaper, with an average sale price of 1.958 €/m2 for 2-bedroom apartments in the city center and 1.835 €/m2 for 3 bedrooms. To rent, the price per square meter is 8.4€ and 7.6€, respectively.