To earn this achievement you will need to do the various jobs offered by The Crew - deliver packages, protect the dealers and hookers etc.
Once your reputation reaches 100, head over to the pawn shop. Speak with the guy in the pawn shop and he will make you an offer to work for The Crew permanently. Accept the offer and you'll earn this achievement and then see the game over screen.
If you've not reached the end of the game (day 21) when you do this, you can simply rewind time from the main menu and replay this day, ignoring the offer to work for The Crew and continue on with the main story.