Why do the players need a ship? How do you want them to use the ship?
You may not have easy access to it but Starships of the Galaxy does mention the ways PCs might acquire a starship. When you're looking at starships take a look at the Challenge Level (CL) listed for them after removing the crew component (+0 for normal, +1 for skilled, +2 for expert crew qualities) and remember that it is suggested that you take half that value off of the effective CL of any opponents faced using the vehicle.
For a "group's ship" I'd really suggest keeping the CL of the ship down. Your stock YT-1300 is already CL6. You want one that can hold everyone between crew+passengers. If you plan on using it for vehicle combat you may want to check ship roles and ask what you'd have each character doing during a fight.