This work is available after “Shadow” in Little Jacob's mission line. Select “Job” from Little Jacob's Phonebook menu to accept a job from him. There are a total of 10 deliveries available, all of which take place in Dukes and Broker. Each one consists of first entering the vehicle that contains the package and then delivering said package. There is sometimes a time limit, but if none is given you will instead meet some resistance—in the form of a rival gang or the police—upon stashing the package or handing it over to the buyers.
You don't have to deliver the package in the jalopy that it's found in, so be sure to have a fast car on hand in case it's a timed delivery. If there is no time limit, you will then have to face either a rival gang or the police. If it's a rival gang, you'll start off surrounded, so quickly sprint away to be out of the thick of it, switch to a powerful gun and wipe them out. If it's the LCPD you're facing, don't make matters worse by firing back at them; a two-star wanted level is much easier to shake than a three-star, so flee the scene and leave the buyers to deal with the cops.
The package for the last job will be in a Huntley Sport; that's your reward, so be sure to park it in front of one of your safe houses.