If you have enough cash in No Man's Sky, you can live a life of luxury, buy the best ships and freighters you want, and pick up the coolest multi-tools, too. Unfortunately, things aren't so easy and you have to work your way to riches.
If things weren't hard enough, you also need to find plenty of nanite clusters so you can buy all the technology upgrades you need so I'll explain a few different methods that you can use to get all the units and nanites you'll ever need!
Collect Sac Venom and Gravitino Balls
Different planets have different kinds of rare commodities. For instance, only toxic planets contain Sac Venom and only high security worlds have Gravitino Balls. Most of these items only sell for around 10,000 credits a piece which is small change compared to some other moneymaking methods. By the way, picking up Sac Venom or Gravitino Balls have the side effect of alerting sentinels so watch out!
Raid supply depots
Supply depots are caches of valuable materials found on planet surfaces and are guarded by nearby sentinels. If you take them out, you can find some valuable items like Herox that you can sell for a decent profit.
Destroy enemy pirates with bounties
Sometimes, you can get 100,000, 200,000, or 300,000 units for killing a pirate bounty. It seems random whether you'll actually get the money or not so it could be a bug. Anyway, if you're feeling lucky, go ahead and take out some pirates!
Unearth crates near crashed freighters
You might find colossal freighters on planet surfaces. In fact, you're sure to find one in your starting system while searching for the warp drive blueprint. These freighters have several containers around that can contain money or extremely valuable commodities.
Upload your discoveries for nanites
If you have a lot of discoveries under your belt, don't forget to go to your discoveries tab and upload them. You'll receive a few nanites and your planet names will be uploaded to the servers so if you want to name any planets then don't forget to do this.
Complete guild missions
Guild missions are one of the quickest ways to acquire nanite clusters. At first, you won't have standing with any of the guilds but the mission board will still likely have at least one or two missions that you can accomplish for nanites. There's a large variety of missions like taking photos, scanning things, delivering goods, and destroying sentinels. Complete enough missions and your reputation will become high enough to take on even more fruitful missions.
Buy materials and get crafting
You can always talk to other pilots and see what they have for sale. Sometimes, they sell materials that you can use to create trade commodities just like the materials you would otherwise grow at your farm. You might find other useful items like glass as well. By the way, you get the blueprints for these commodities by doing missions for the base scientist or by raiding manufacturing facilities. Always keep an eye out for what people have for sale in case you spot a good deal so you can turn in a healthy profit.
Scan stuff with the upgraded scanner
On board space stations, you can purchase scanner upgrades that substantially increase the amount of cash that you get for scanning plants and animals. You can stack up to three scanner modules on your multi-tool before the technology becomes overloaded and you have to remove one. If you have scanner upgrades stacked up then scanning stuff can become a serious source of sweet cash.
Use someone else's farm
At this time, you can only visit another player's farm if you're on the same platform as them. The Galactic Hub has a good amount of community farms but you can also go to your friends' farms if they play on the same platform as you. Once there, you make money exactly the same way as if it was your own farm so just create valuable items; provided you have their blueprints, of course.
Create your own farm
The single best way to make money in No Man's Sky is to make a farm so you can create valuable trade commodities (like living glass or circuit boards) that sell for a serious amount of money. Some sell for around 500,000 to 15 million credits a piece. All you have to do is place a hydroponic tray then the plant of your choice on top of it and wait for it to grow.
During the farming missions while building your base, you get these plant recipes: Coprite Flower (Coprite), Frostwort (Frost Crystal), Solar Vine (Solanium), Fungal Cluster (Fungal Mould), Gamma Weed (Gamma Root), Echinocactus (Cactus Flesh), and Star Bramble (Star Bulb). You should harvest these materials to create the appropriate trade commodities. For example, a circuit board sells for around a million units and requires 100 Frost Crystals, 200 Solanium, 100 Cactus Flesh, and 200 Star Bulbs to create. Also, make sure you have the trade commodity recipes unlocked. You can get these by recruiting a scientist to your base and completing their quest line.