From Revenue
"A first time buyer is a person, (or, where there is more than one buyer, each of such persons):
* who has not on any previous occasion, either individually or jointly, purchased or built on his/her own behalf a house (in Ireland or abroad) and
* where the property purchased is occupied by the purchaser, or a person on his behalf, as his/her only or principal place of residence and
* where no rent, other than rent obtained under rent a room arrangements, is derived from the property for a period of two years from the date of the purchase. This relief is subject to clawback provisions. "
mf