Open up the aquanox/dat/sav folder. With a text editor, open up the file player_start.des In it you can change the amount of credits you start the game with. I used 999999 as my amount and it worked fine. If you try more, it might crash. After all, you will see a warning "Do not modify" at the top of the file, so don't get greedy. This amount will carry over into the missions as you progress. You can buy any ship and weapons that are available.