What are some of "privileged" jobs that the slaves can hold?

From the text:

The shoemaking and mending, the blacksmithing, cartwrighting, coopering, weaving, and grain-grinding, were all performed by the slaves on the home plantation. The whole place wore a business-like aspect very unlike the neighboring farms. The number of houses, too, conspired to give it advantage over the neighboring farms. It was called by the slaves the Great House Farm. Few privileges were esteemed higher, by the slaves of the out-farms, than that of being selected to do errands at the Great House Farm. It was associated in their minds with greatness. A representative could not be prouder of his election to a seat in the American Congress, than a slave on one of the out-farms would be of his election to do errands at the Great House Farm. They regarded it as evidence of great confidence reposed in them by their overseers; and it was on this account, as well as a constant desire to be out of the field from under the driver's lash, that they esteemed it a high privilege, one worth careful living for.