I think a great alternate form of income could be a bounty hunting side-quest system. There could possibly be prison stations throughout the systems that would contact your ship we a bounty is placed. You would then have to track down the target, apprehend him, and drop him off at a prison station. Kind of like Killjoys (new tv show). Sorry I've been watching that show a lot recently. It's really great and would make for some cool gameplay mechanics.
