Well, the best way to make money in the beginning is not to spend it so easy; those health hypos are kind of a trap, stick to bandages whenever possible xD
But yeah, you get a ton of money with jack quicksilver's quest if you survive, from selling weapons/getting a reward. Other than kolmeiers stash in junkyard, I don't know of much non-quest money tho. If you have lockpicking/hacking, there's a locker in private quarters with gobs of money. And if you're desperate, pickpocketing also gives gobs of money (nvm, just check you need a decent amount to steal credits).
You could wander around north (up and right) of the train station (don't go south!!!). This is the main quest general direction, but there's some tunnels with stalkers that are very weak.
Also, make sure to sell to every vendor. Leather and rathound organs give a surprising amount when you sell them to quinton in agronomy.
