There's a bit of misinformation floating about in regards to the New South Wales Penal Colony at Botany Bay.
Initially, the first settlers were Free Men. They established the basic camp, and then the town.
When the convicts began to pour in, they were put to work building and attending to farming, including crops.
There was a reasonable mix of trades within the free settlers, and some of the convicts had skills required for construction and maintenance.
Not all of the convicts were criminals, in the modern day accepted sense. Some were simply the occupants of the Poor Houses in England, and others were political prisoners, particularly among the Irish. In many cases Irish men who had been involved in the Agrarian Revolts in Ireland, or were members of what the English considered to be subversive groups, such as The White Boys, were transported for Life, so that they could never return to Ireland and stir up trouble. The English Government even paid for their families to travel to Australia free of charge, as a further incentive to stay.
All in all, those prisoners who behaved themselves were generally treated well by their free settler bosses and went on the become land owners or business proprietors themselves.