There should be an NPC shop selling some basic items in every NPC starting city (those on a race's homeworld). Everything else (currently that's ships, vehicles, space stations, facilities and raw materials) will have to be bought from other players.
I suggest you either go on IRC and talk to the people in #swc-traders, or check on this section of the boards: http://www.swcombine.com/forum/index.php?board=1 The RPG Centre also has all of the forums for buying and selling.
"Somewhere, there's a bullet with your name on it. The trick is to die of age before it finds you"