As I posted below and also public transport as mentioned in other comments Change zoning rules. Incentives for co-living. Reduce flat sizes. Rebuilt office spa

As I posted below and also public transport as mentioned in other comments Change zoning rules. Incentives for co-living. Reduce flat sizes. Rebuilt office spaces. Or look to Vienna: a big stock of goverment-owned flats with low prices which makes it hard to charge more than those.