The enemies' resistance rises fast...you can do either the missions for mo' money on the stations or the other more common method usually was jumpgate-camping
(if you are focused only on the main mission it'll be very hard later on). Uhm there even exist a random mission with some nice reward (1 mio).
Uhm can't remember exactly but i think there was a location right at the beginning before getting Corsair. on one side of a jumpgate there was a patrol waiting for you (plot related?!). You could kill it, jump back/forth..kill it again and so on. Although they weren't that bad against your crappy ships + gear at least at the beginning.
As said quite some time ago...maybe you should give it a try. The aliens and some other scripted events were hell without some 'other' income.
You could even (with some better equipment and maybe + Corsair) park at some random jumpgate, set your fighter guarding your mo-ship...shoot some ships which are coming from the jumpgate and after some time, everything is hostile. Go shopping / or do whatever you want and let them have fun for some 'hours' ..
(I think there were good locations right in some beginning sectors but can't remember them. There weren't not really factions in SW2 so it doesn't matter if you beat the living *** out of some sector and go elsewhere ^^)