If you buy a couple of 2x1 TNT terraforms, you can check multiple adjacent caves and "undo turn" if the cave contains a whole load of nothing. TNT terraforms are a faster way to make tunnels in general.
A party temporarily increases the colony morale, which can be useful if you want to take in more colonists, but can't due to low colony morale.
The cooldown for these is pretty long and they're semi-expensive so it's usually better to celebrate once you're done with mission goals.
A crippling dept is undesirable, but if that might help you avoid a certain death or win a mission just in time, you might as well.
Other than that, there aren't too many things that money can buy to create a large income stream.