You don't take up 'jobs' ala Ryo in Shenmue where it's basically like a simulation...you can see people with sidequest marks over their heads and by helping them with their individual stories (ranging from finding a panty thief to playing the role of Detective Poirot in a cafe murder), you gain skills, money and experience.
There are loads of side-activities but then again, time doesn't move so they're not 'jobs'. They're minigames that, if you're really good in your skills as a player, reward you with money. These range from Mahjong, Shogi, Golf, Wrestling, Managing a wrestler's career, managing a Hostess' career, etc. The thing about them is that they're not intrusive at all. You can just ignore them and head to the next destination on the map and plow through the main story. As Yahtzee from Zero Punctuation said, "I think there's something to be said about a game when you can plow through the main plot and not even touch half the content"
Kamurocho is the main setting of the game. It's less of a city and more of a district. Think of Hong Kong from Shenmue 2. It looks open world but the seams are there, if you know where to look.
