Expensive for Budapest, but as you said, not much room for new build in District 1...3,500Euro per square meter. It will probably be a corporate let (hopefully) and if the figures stack up with regard to rental in the area, it should be ok. I'm not too worried about the delay as it has cost me no more than the deposit so far and hopefully there is some (limited,I know) capital appreciation by the time we exchange contracts.
Do you know anything about the rental market in this area at the moment