Archeology is my current favorite money maker. Aside from the high value treasure that can be found in the temple & sometimes fishing on the island, the artifacts from the dig sites can be worth a fair bit once authenticated. And once they've mastered the skill they will start getting artifacts in the mail to authenticate & get paid well for doing it.
I also like to have them master the rocket science skill so they can go to Sixam & sell the rocks they find there & start a garden of alien harvestables that are worth more than home world plants, but it takes a few trips just to make back what they invested in buying & upgrading the rocket.
