To new players: You can have 2 Large freighters with the Hatikvah Trade Revolution
This video was done with no DLC.
When you do the Hatikvah Trade Revolution story arc, Dal Basta will task you to plant two spacesuit bombs on a pier. Proceed to the designated station, and just wait and observe. The first Pelican should be on its way to the station to dock, the names of these ship will be different from others. Instead of SCA Pelican, it will simply have the name "Pelican Sentinel". But even if you don't see and identify them, just keep waiting, don't plant the spacesuit bombs.
When the first ship arrives and successful docks at the station, Dal Basta will tell you that you failed, but tells you there's another one coming. At this moment, you can choose to plant the spacesuit bombs to succeed the mission, or choose to completely ignore it and fail. Either way, the story arc will continue to next mission and there are no lasting effects. There is no 3rd ship.
If you've already completed the mission and you planted the spacesuit bombs with the first ship, you can go back to the station and the ship should still be there. But if you waited for the second ship, there will be two Pelican Sentinels that are FOREVER docked to that station. They will not leave or try to get away if attacked. They also have weirdly low boarding resistance, despite having crew workers (should be a little higher). Board each ship with enough marines to overwhelm the crew. Despite the cutscene asking for backup, there is no one coming to help them. Just make sure you don't hit the station they are docked with, or it will join the fight.
These Pelicans are not the best freighters, but having them very early in a fresh start will help you a significantly (specially if you don't like using cheats). They will have items in their cargo space for you to do as you wish and they are somewhat equipped. So you can put them to work any way you want, or strip and sell them to a wharf.
The frigate I am using in this video is the derelict Osprey Vanguard in Company Regard, it has space for 15 marines.