For a group of 6, i would suggest a Transport and maybe 1 or 2 person escort fighter. if you want them all in one ship you could go with a medium transport, with a "lampray" style dock for a fighter... or the wayfarer

one of the ideas, since it has a lot of support material online is the Mobquet Medium Transport

Someday i might do a privateer game and give the players a Correllian DP20 Gunship/Frigate, there was a WEG book that had a simple deck plan for that ship

I have a new team that we agreed to start with the Gozanti-Class frigate. It has attachments for additional ships. Since one of the PCs has a Z-95 from a previous adventure, it was important to have this capability. The players like the look of this ship much better than the Wayfarer. In my game, I disabled one set of lasers (back story damage) to downgrade the oomph and make it more in line with a starting ship.

The ship is in the AOR book so that is where we are getting the stats. It fits very well with smuggling and general adventuring.

To make the Citadel more customizable - especially if you want to use it as a freighter - we ruled that it has 10 cabins and a small hold. The hold can carry 50 Encumbrance. Each cabin can be set up with either a single bunk and 15 Encumbrance storage (whre the bottom bunk would be) or two bunks.

The standard configuration given in the book is for maximum passenger capacity so only the three rooms for the crew are outfitted with single bunk/cargo rooms ([3*15]+50=95 Encumbrance]. Our group is looking to have six single bunk/cargo rooms to give it equivalent cargo carrying to a YT-2400 ([6*15]+50=140 Encumbrance).

I also allow the external clamps to hold cargo pods instead of fighters. Hey, some freighter captains actually try to haul freight!