what would {qaDIl} mean?

Is it like in English that you gave somebody the money for their job, or
does it sound awkward as if I buy a person?

I think it would be context-dependent. In the context of slavery, hiring someone, acquiring a sports-player's contract, and so on, it would mean SoH qaDIl, where the speaker has paid money to acquire the person they're speaking to. In other contexts it would be an instance of the prefix trick, the long form of which would be SoHvaD jIDIl or SoHvaD vIDIl, where the speaker has paid for something for the benefit of the person they're speaking to.

Undoubtedly, there are those immature people who, when being treated to a meal in a restaurant and their host casually says qaDIl, waggle their eyebrows, grin, and ask if they're supposed to be a slave or something. The payer is then perfectly justified to roll their eyes and wonder if they should have bothered treating the person to lunch after all.

And while talking about that... is there a word for "hire" a person,
i.e. charging him to do a paid job? I'm sure that {ngIp} is strange.

None I can think of. ngIp is obviously wrong. I might use something like gheS 'e' DIl pay for [someone] to take on duties [of some job].

-- 
SuStel
http://trimboli.name