It’s all about the green salad.
Money makes the world go round, and that logic applies to No Man’s Sky as well. Why do you want Units? Well, you want Units so that you can buy new ships, and new ships comes with better upgrades and more inventory slots. Units also allow you to buy Exosuit upgrades, which give you more inventory slots as well. Inventory management is extremely painful in this game, so you’ll want all the help you can get.
Here’s a pro tip for getting rich in the galaxy: mine all the Emeril you can find, and then sell it off at the Galactic Trade terminal. Emeril is one of the most valuable resources I’ve come across in the game so far, and they’re not terribly rare. From my experience, they’re usually found on moons or on planets with desolate of peaceful weather. Planets devoid of any wildlife are also a good bet for finding Emeril.
The reason why Emeril is so good for getting rich in No Man’s Sky is because it’s valuable regardless of whether its price is above or slightly below the galactic average. Even in a star system with a lower markup for Emeril, you can easily make about 400,000 to 500,000 Units from selling four stacks of Emeril. Gold will fetch you a similar sum as well, but these are a little harder to come by. The great thing about Emeril is that it often comes in huge mountains too. So once you find one, be sure to mine all of it, and check below the ground too.
You can also make easy money by crafting Bypass Chips and selling them off, but the gains are a lot lower during the beginning of the game where you have less inventory slots. If you can clear out your inventory, you’ll be able to carry a ridiculous amount of Emeril, and sell it off in one go.
There are much more valuable resources out there right now, but Emeril is relatively common, and it isn’t used in a lot of crafting recipes, so you can sell it off without worry. Once you spot a mountain of green, get off your ship and start mining.