How to unlock: talk to PAM robot in the Railroad HQ (M6,2)
During this quest, you will go to the Red Rocket Trucker Shop near Sanctuary. You must prepare the defenses of the place by constructing a defense with 10 defense points. The easiest way to do it is by building two simple cannons. You can use the materials available on the station.
Important: until you will have settlers in any village, building the wooden outpost will not add you any defense points. Someone must be able to use it. Other defense elements, except for simple cannons, require electricity, so make sure that you have enough materials. What's interesting, after completing the mission objective you can pick up the turrets (without destroying them) and place them in any other settlement you want to improve.
After constructing the required upgrades, go back to the questgiver. Caretaker will appear there, you can receive other minor quests from him.
Quest rewards: experience, 200 bottlecaps, quest Jackpot: Medford Memorial Hospital