I’ve found on Airbnb, maybe 3/4 months in advance. The airbnb was around 650€ per months but when I arrive the owner made a deal with me. I’m paying cash for a lower rent as I’m staying for about 6 months or so.

I’m at Kypseli, it’s a less touristic area, far more better than the city center. I would also recommend Pangrati

Athens in Greece. 550€/months for a 35m2. It’s a nice renovated studio with everything I need (and good internet). This city is super nice to escape on week-ends due to the proximity of nature, from islands to mountains.