Rogue
The opening line in the Player's Handbook states "Rogues have little in common with one another." This is completely wrong.
Rogues most certainly have much in common with each other. Beyond the obvious need to work outside of the natural framework of imposed laws, the PHB gives a long list of potential professions of rogues. Rogues in ["Arthea"] are well organised; without organisation there would be no organised crime. Some criminal gangs in Arthea really like organised crime.
There are differing degrees to this organisation. ["Ticetia"] has the best organised criminals. This situation has persisted from the days when the crown of Arthea was passed to the Ticetians. There is no big city that isn't controlled by a multitude of criminal gangs and organisations. This behaviour has spread to ["Caldonacia"] too, and is almost as bad. In these places it is virtually impossible to operate as a thief alone. If the organised criminals find out, they make no habit of leniency. Only in the former Empire is it still possible to be a solo rogue.
This doesn't make it impossible to form a new criminal organisation in the north. New gangs turn up all the time, often from some of the pieces of a group that could no longer agree. This can make the choice of rogues guild an important one.
If an individual is planning a career as a rogue, then they would do well to learn their trade from those who are already working it. Rogues can, of course, train themselves - but learning is far quicker when instructed by a master.