You can build a mineral extraction base that will passively produce 10's of millions of credits in the form of activated indium. Here's what you need:
Get the blueprint for the surveying multitool upgrade from the space anomaly. This will allow you to locate resource nodes on "hotspots" that can be mined via mineral/gas extractors in a base.
Get the blueprints for mineral extractors, pipelines, supply depots, and electromagnetic power generators, and wires(?) from the space anomaly. These are the core components of an extraction base.
Gather a quantity of basic materials: metal plates, metallic ferrite, chromatic metal, ferrite dust. A few hundred metal plates and a full 10k stack of each material - don't mine them, buy them from stations whenever you see them. (Not sure if I'm leaving anything out, but you can check the blueprints.) You may need to buy copper and refine it to produce the amount of chromatic metal you will need.
With your fully upgraded hyperdrive (upgrades sold in the space anomaly), head to a system that has activated indium. Scan for a planet that has it, and then land anywhere. Now you need to toggle your multitool to "survey" mode and track down an activated indium deposit. You want at least "A" class, though "S" class would be ideal. Once you find the indium, survey all of the adjacent resource nodes to find an electromagnetic power node. Basically, walk in a circle around the indium node at about 500 units distance. If you manage to find a power resource node, mark it and then plant your base computer halfway between the indium and the power source.
Build a power plant. Use your multitool survey scanner to read the power level of the electromagnetic field resource - you don't have to build in the exact center of the node, but just close enough to get a decent amount of power from your generators. Build 50+ electromagnetic generators and link them with wires.
Start building your mineral extractors close enough to the center of the indium resource node to get maximum output.
Rune wires from the power plant to your extractors and link them all. A decent sized base can have more than 100 of these.
7 Build a cluster of supply depots next to the extractors - you don't need a lot, start with 10-20 depending on how often you plan to return to this base.
That's it. The extraction base will work all the time, day and night, even when you're not there. Build a teleporter so you can reach it from anywhere. Each 10k stack of activated indium will sell for about 8 million.