RTE have reported on a survey of ghost estates around ireland, and have produced a quite detailed summary of their findings.
the cork city and county results are on page 5 of the pdf.
they say there are 825 completed and occupied, and 419 completed but unoccupied houses in ghost estates in cork city, leaving 720 unfinished houses. (total 1964)
there are 7493 completed and occupied, and 2681 completed but unoccupied houses in ghost estates in cork county, leaving 8507 unfinished houses. (total 18681)
number for city doesn't seem too bad, but the county seems shocking