This is my first written solution to acquiring an achievement.
Edit: you have to complete The Final Descent quest before you can start Served Cold(confirmed)
Step 1.) Head south out of raven rock to Old Attius Farm. The icon on the map that looks like a sicker and some wheat.
Step 2.) Once youve gotten there, there should be a fight going on. Help the poor Captain Veleth fight the ash spawn.
Step 3.) Get the quest March of the Dead from Captain Veleth. After acquiring the quest search the ash piles of the Fallen enemies to find a note. Give said note to the captain.
Step 4.) The captain wants you to go kill someone in Fort Frostmoth. It's located to the east of Old Attius Farm Head there and kill said target. The fort is fairly straight-forward. Once the target is eliminated, head back to the captain and finish the quest.
Step 5.) Captain Veleth should have a new quest for you called Served Cold. He tells you to go speak to Adril Arano. Adril then sends you to Geldis Sadri.
Step 6.) Geldis sends you to wait in Ulen Ancestral Tomb for a secret visitor in the dead of night. As soon as you start a conversation with the visitor, your quest will update to report back to Adril.
Step 7.) Adril tells you to go find evidence in the Severin Manor. What you seek is a note called the Ulen Matters in the safe on the back-left side of the room that is straight as you walk down the stairs. Once you have the note, return to Adril.
Step 8.) Adril tells you to meet redoran guards at Ashfallow Citadel. Once there go in and eliminate your targets. There are several floor traps so be careful. Once the targets are eliminated head back Adril.
Step 9.) Final step. Adril tells you to follow him to the councilman. After a brief conversation between the two the councilman asks to speak to you. Once the dialog ends, the quest Served Cold is completed and you should be the proud owned of a house in Raven Rock as well as a proud owner of that sweet 20 G's.