If you put this hypothetical 90k euro house up for sale at a public auction tomorrow, what would it sell for? 50k? 70k? Real assets are usually sale-able, albeit perhaps for less than the owner thinks the asset is worth.
> Move to where? Another city? Another country? Unemployment is everywhere in Greece.
Since Greece is still in the EU, you can move to any member country right? UK, Germany, France? Certainly there must be places in the EU where the economy is better and there are more opportunities. People have been migrating around the world chasing economic opportunities for thousands of years. A million Syrians just traveled through Greece on their way north in search of this.
> Government passes the law and our house has a value of 500.000 (because of the area around it). Now out of the blue we have to pay property tax. What do we do?
It seems that what has effectively happened is that the Greek Government has decided to confiscate a large part of the country's wealth through extremely high property tax rates. As other posters on this thread have mentioned, if the tax rate is 1% but the appraised value is 3x the actual market value, then the real tax rate is 3% and your Government is just playing games to try and hide the confiscation.
Personally I would vote for revolution - national default, totally new political leadership - and start to rebuild the country from scratch. Anything is better than decades of externally enforced austerity crippling a country's spirit as reflected in everything I read these days about Greece.