I always used ships that have aiming guidance , even though they were less powerful :P

Ah, guess you're at the portal scan mission in Farnham's Legend.

There's no need to sell anything, hunting pirates for a while will get you all the money you need and more. Some will drop missiles when killed, and for every hit they take after the shield is down there is a chance they'll leave you the ship, wich you can then resell at any friendly dock station. It's the fastest way to make money until you can afford a station complex.

And as a side note, to be fair the campaign is not easy at all, there are some very frustrating scripted events so don't get discouraged by them. Regular combat with pirate and Commonwealth fighters is definitely easier.

+1. Very good advice there.