Money can be pretty hard to come by, but there is a way to gain access to an infinite amount of funds:

Simply go to the Junk Shop in Scrap (located in the lower right hand corner) and pay the shopkeeper for your choice of items (you can pick 7.) After taking your items from the barrels and boxes, go and talk to the shopkeeper again. Tell him you'd like to sell, and point to the last item on the list, the Hyperion Bazooka. Press the accept button several times, regardless of whether or not you actually have one.

Then, go back to the room where you picked your items: You can now pick 7 more! This can be repeated as often as you like. To get infinite money, head to the barrel in the middle left and keep searching. Pretty frequently, you should find Hard Leather, which can be sold in Koorong for 45 credits each. Repeat until you have about 50 or so Hard Leathers, and you can make a fortune!

You can also use this to find some average-strength equipment (simply look all around the room) with little effort. You will have to pay every time you leave and come back to get more, however (it's about 600 credits, I think.)

Note: After a while, the goods offered in the Junk Shop will increase in value, and Hard Leather will no longer be offered. When this happens, for the Infinite Money, simply go to the upper left-hand box and get the various swords there. EACH of these swords can be sold in Nakajima Robotics, in Shrike, for even more money than the Hard Leather!