Originally Posted by
selek
It would be the same as purchasing any other Elite profession- you'd have to meet all the prerequisites for that profession and spend one advancement (five picks) to purchase the new profession.
(There's a cheat there, of course). Your character can purchase the Starship Duty edge a second time, and wave the prerequisites.
Once in the new profession, he purchases Professional abilities and such normally.
In the normal course of events, however, you'd more likely start him as a helmsman and THEN transfer him to the command branch.