Get these SVs and the Black market by advancing through the story line by defeating the rankers.
During the map menu area where you have to select a location to travel to(Hanger, Mechanic, etc.) Rotate the right analog stick clockwise as many times as possible, you will start moving upwards. The higher you go, the more credits you will gain. You will gain 10 credits then 100 and lastly 1,ooo credits all in a day. You can repeat this trick only once a day earning a total of 1,110 credits each day.