A fast way to earn credits at the beginning is to ship some rare goods. These can be found all over the place in certain stations and are highlighted yellow in the list. They give more profit, the further you travel, running into a maximum at around 120-150LY.
However, there are 2 Clusters which can be "harvested" perfectly with a Cobra with 40t of cargo and the best FSD for the travel in between.
A hint for those who want find the places themselves: Go to the place where you started with the Sidewinder in original Elite and some systems around, then travel to the space inhabited by Coalition in Crossfire and surrounding systems....
Lave - Cluster:
- Lave - Lave Station
- Diso - Shifnalport
- Uszaa - Guest Installation
- Leesti - George Lucas (caution: 2 rares, Evil Juice is illegal in some systems)
- Orrere - Sharon Lee Free Market
Altair - Cluster:
- Altair - Solo Orbiter
- Zeesse - Nicollier Hangar
- George Pantazis - Zamka Platform
- Epsilon Indi - Mansfield Orbiter
If you don't get a full hold in Altair, you could go to a 3rd cluster ~70LY away. These goods would also go direction Lave for the distance, ofc:
Fujin - Cluster:
- 39 Tauri - Porta
- Fujin - Futen Spaceport
- Witchhaul - Hornby Terminal
- Wolf 1201 - Saunders's Dive
The profit you make is around 12-15k per ton