Sorry if my english is bad, It is not my language. Sometimes I might mean things other than I wrote
Edit 1: I mean this as a job till I am older and have a full time job, if I have a fulltime job, I will keep this as a side job (if it is still possible)
Signature campaigns are good but I don't think you can earn enough to call it a job. I just use one to add a little extra bitcoins to my holdings to boost what I have a little, but it just amounts to a few dollars a week. You may want to consider getting into trading to earn a little more.
The best thing to do is to save more bitcoin and use bitcoin for other activity that you can increase your bitcoin and earn.. if you can study and get a courses of internet marketing this is best and use your bitcoin to buy domain and hosting and promote your own website and offers.. Like CPA networks who are paying in bitcoin like peerfly that can help you earn more than signature campaign.