Brock: (Anime) Pokemon Breeder; (Game) Occasional Fossil Digger
Lt. Surge: Is a pilot; was a soldier before
Erika: A student of the art of flower arranging
Koga (Former): Teacher of Ninjutsu
Giovanni: Team Rocket Leader
Green: N/A; most likely too young to hold down a second job
Bugsy: An insect Pokemon researcher.
Whitney: N/A (making kids cry with her Milktank)
Morty: Studies and researches Legendary Pokemon related to the Towers of Ecruteak; also a seer
Jasmine: Unofficial; takes care of Amphy at the lighthouse
Pryce: Retired from unknown job.
Brawly: Martial Artist
Wattson: Founder of Mauville City, also town planner
Norman: Negligent parent; call social services
Winona: (manga) Supervisor of all Hoenn Gym Leaders
Tate and Liza: N/A; likely too young
Wallace: Juan's pupil, runs the whole of Sootopolis.
Juan: Wallace's mentor/instructor, accomplished Pokemon co-ordinator
Maylene: Martial Artist
Wake: A charitable man (uses the prize money he gets from competitive Pokémon battles to help the unfortunate. Just like Norman.)
Fantina: Contest Expert/Performer
Candice: Teacher in Snowpoint City
Volkner: engineer; built the solar panel walkways in Sunnyshore City
Cilan, Chili and Cress: Run a Restaurant; they are waiters, cooks and tea connoisseurs.
Lenora: Archaeologist; librarian
Elesa: Fashion model; also makes TV appearances
Clay: Businessman & miner
Drayden: Mayor of Opelucid City and Iris' mentor
Iris: N/A; too young
Roxie: Rockstar and singer
Grant: Athlete - rock climber
Korrina: Athlete - Rollerblader; guardian of Mega-evolution secrets; PR video star
Valerie: Designer and model from the Johto region
Olympia: N/A; possibly seer due to her psychic powers
Wulfric: Unofficial; takes care of the Pokemon in Pokemon village.
There are quiet a few (around Johto and Kalos) that I didn't quite get, post if you think I missed something.
As a matter of discrepancies, there are a few like Brock's role as a Breeder in the anime, which was not mentioned in the game, and Winona's job as supervisor in the manga.
Hope I helped!