as playing an role-playing game you can find some available profession, so does in GetBackers. each character have their own role and duty depend on the profession they had chosen. Here i enlisted those exclusive jobs in GB world:

Dakkanya
the main job of dakkanya is to retrieve any lost/stolen goods, but not stealing them. what they do is basically take anything which are not on its proper place or owner, then return it to its true owner. (ban and ginji, shido, emishi)

Hakobiya
i think it's equal with professional deliverymen. they will carry any luggage to its destination at save, certainly it's highly-priced or top secret luggage. (akabane, himiko, makuruma)

Ubaiya
on the contrary of dakkanya, ubaiya's job is to steal something from its true owner. they were quite resemble to dorobo (thief) in our real life. (formerly ban, himiko, yamato and wan pore)

Mamoriya
you can hire these people to protect yourself or something you own, esp. if you feel threatened. let me say they are more less bodyguards. (hishiki ryudo, miroku natsuhiko and his 6 alters)

Annaiya
often get lost like ginji? hire these ones because they are very reliable guide. they will help you get into places you don't know well. (kazuki, kagenuma sara)

Chuukaiya
or middlemen, they work as agents for the clients and anyone hired for the job. of course they will get reward for their service. (HEVN)

Shimatsuya
these people were hired to ensure that everything goes as it's expected, including to get rid off certain targets or also known as koroshiya. (kurobe brothers)

Kusuriya
drug dealer, physician, doctor, or anything else you'd like to call them. obviously they sell drugs and cure sick people. (randou gen and his granddaughter ren).