It says Fuck off because Cook doesn't trust The Kid and thinks The Kid just some overzealous/arrogant punk forcing his way into a world he doesn't understand.
But as we learn, The Kid does understand it very well.
The Kid still gets to go on the job not only because he's doing it for Standard and his wife, showing his arrogance and determination as part of his strengths (instead of the usual weakness it invokes in most characters) but because he presents to Cook that he'll do it for free, meaning The Kid can be just more free muscle for Cook's job.