The average home buyer cannot affordably purchase the majority of homes in three-quarters of Sydney, new research from UNSW's City Futures Research Centre shows.

As recently as 10 years ago buyers could comfortably house hunt in swathes of the west, south and north-west for affordable options. Now only a sliver of affordability remains, including a small collection of postcodes toward Penrith and in the Canterbury-Bankstown area. That sliver will almost certainly disappear as new…