All I did was select the Interception fixer contract "Deadly Loop", from the fixer contracts app on your phone. Make sure you have the GL-94 pump action grenade launcher, if you don't have it buy form a gun shop. I'm not sure on the price, but money is easy in this game so that should not be an issue. Also I'm not sure when this contract becomes available im on act 4 mission 2.
This contract involves "taking down" killing two targets. When you start there will be a sports car parked to to your right facing the wrong way in traffic. Hop in and go the way the car is facing, take the first right underneath the L station, then your almost immediate left into the ally, Follow the ally to the next block and stop and get out just outside the next ally. Targets should be turning down the ally headed straight for you. Pull out your launcher take aim and blast the first car, the second one will squeeze though wherever he can so blast him too. Mission complete. If you miss, run out of ammo, or the cops get called. Blow yourself up cops will be gone and ammo refilled.
After you complete this once you will need to set a waypoint to be able to play again. This can be done in 27 sec, takes about a min to run back. Can be done from 0 in a little over an hour, once you get the rhythm down its quick.