After receiving his education he moved to Queensland where he was said to have worked as a rural labourer before becoming postmaster at Windorah then settling in Thargomindah.
It was here that Leahy held a partnership in a cordial factory and, with his brother Patrick, became part-owner of the Thargomindah Herald.
From 1886 until 1889 he was also the proprietor of the Royal Hotel which was located in the main street of the town.