To be a Bounty Hunter, your level must be over 40 and you need to collect the Mark of the Guildsman, the Mark of Prosperity, and the Mark of the Searcher.
But what is this, you level is not high enough and you haven't even collected all of the marks. Are you deaf? Come back after collecting the marks and after more training. If you fulfill these obligations I will change your occupation to a Bounty Hunter.