When buying ships from a faction do you have to buy the data card as well as the craft?

Most likely not. When your buying a ship, you get the ship not a datacard. Although most faction do sell em. or rent em.

You only want the DC if you have a shipyard or factory to have it assigned to, the necessary RMs to produce, and the other conditions listed on the Production rules page.

Otherwise, buying a ship from a production faction is like buying a ship from anyone else.

ok thanks guys