I voted for the first option because while that's not how Cain currently earns his living, it's what he aspires to. It might be a bit implausible if he was a full-fledged thaumaturge after approximately a year or two of training, so I imagine that he supports himself by doing odd-jobs until he/I can feel more comfortable with the idea of exploration, adventure and danger.
He usually hangs around in Ul'dah or Limsa Lominsa.
He usually hangs around in Ul'dah or Limsa Lominsa.