Just start doing odd jobs that you can find at bases...(search and destroy, kill all ships, etc....)

Mining is a waste of time.

Go to Colorado, get a Rhino, blow up rocks in the Copperton field next to Pueblo Station, sell the copper you get to Pueblo for about...er... can't remember, but a lot of $money$.
Or, alternatively, cheat.

There was one cheesy tactic, blowing up the storage depots in NY, I think they're near Fort Bush, grab the loot and sell it. It'll hurt your rep with the Police, but that gets fixed at the start of the next story mission anyway

"There are 10 kinds of people in this world: those who understand binary and those who don't"

@darkstone, their are about 6 cargo bays inside new york system... destroy them all, and you can start missions for outcast and maybe already for rogues from buffalo base...

mostly i do pirating, when i'm good enough with rogues and outcast i do cardamine runs from buffalo to manhattan and piracy back and destroy aftre last tradeline the defenders with are fighting with rogues (as usual in that place), after a few rounds you can buy the dagger and start missions for outcast, after 2 missions you can do missions for rogues.

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Spamius Threadius

Just one second after the birth of the Universe, space was flooded with particles and over the next 300 million years stars and galaxies began to evolve into the kind of cosmic landscape that we recognise today. But there's one big problem. We shouldn't really be here. People, planets, stars, galaxies should all be impossible dreams. In theory, nothing should exist.

Loot the badlands wrecks. You've got to be pretty sharp to avoid getting nuked if you're still in the starflier, but you can pick up plenty of guns and even some cardamine if you look closely enought. Blowing up the DSE H-fuel depots at Ft bush is the fastest way. In a defender, you'll make about 10,000 credits a pop selling at Manhattan. And you can do it at least 3 or 4 times too. I did this on my 3rd time playing the storyline and it resulted in even having a significant budget surplus by the end of the game (helped once I realized that torpedos were useless)

Give a man fire and he'll be warm for the night. Set a man on fire and he'll be warm for the rest of his life.- Terry Prachett