Warehouse Chief Ranspo:
To become a Scavenger, you must be at least level 20 and must pass the Test of the Scavenger.
I am satisfied with your level, but it seems that you have not yet passed the Test of the Scavenger. Ask Collector Pippi of the Dwarven village about the Test of the Scavenger. She will tell you everything you need to know about the test in detail. After you have passed the test, come to me. Then I will change your profession to a Scavenger.