Hi Christine,
Sharing a flat or house is not that popular on Antigua unless your one of the medical students attending AUA.
There are plenty of houses and flats available to rent and the best place to find these is on the pin boards at supermarkets like "First Choice" or" Epicurean" these are to large food malls in Antigua. Another place to check is "The Observer" newspaper which you can find on sale in most shops or by the side of the road.