Go and talk to this person (they are in Raven Rock too) and it will unlock Served cold.
* (See below for how to start Final Descent if this does not happen) This will continue the mission (that is relatively a short side quest) that upon completion will have you go back to the Captain, now situated in Raven Rock, who will tell you that 'Adril Arano' wishes to speak with you. After you help him, talk to him and he will ask you to investigate the spawn and the farm and if you find anything to let him know. There you will encounter a Guard captain who is fighting spawn and you will have to help. It is roughly south of Raven Rock town, which you start in, located just left of a mountain range (Making the farm roughly in the middle between raven rock and the bottom of the island). In order to get March of the Dead you have to go to Old Attius Farm (I was out wandering for the locations achievement at the time).
Thanks again to EvilResidentUK and PJ76uk) ( Side Note: As stated in the comments below you seem to be required to have done the side mission 'Final Descent' in Raven Rock mines before being able to start Served cold. I was able to get a house free of charge by completing the side missions.
