I have over 40k credits at level 20 and am now leveling biochem and bioanalysis, and diplomacy. I keep sending my companions to mission to get light points. I also spent 5k on a purple legging for my companion so he wont die from tanking for me. I don't know how I made so much credits without slicing. BTW, I am almost light II now, no dark points at all, and people I helped will constantly mail me credits! So being nice might be the secret. Honestly I have no clue why you have no money.