Just Business is an achievement/trophy in The Knife of Dunwall.
How to Acquire
In order to get this achievement Daud must obtain the information needed from the Rothwild Slaughterhouse.
One option is for Daud to interrogate Bundry Rothwild or Abigail Ames for the information. Alternatively, he may destroy the slaughterhouse in exchange for information from Abigail.