Talk to the guard to be able to join Vault City

Go to Vault City and talk to the guard to the right of the inner city gate. Depending on your stats and skills he will require different things of you in order to join Vault City as a citizen. This will make you a faction member of the Vault City NPC faction. You won't be able to join Vault City as a citizen, however, if you're already a member of another faction. This includes player factions or other NPC factions. So if you're already a member of another faction somewhere else, you'll need to resign there before joining here.

• If your charisma is higher than 8, you can beg the guard to be let in successfully.
• If this is not the case, he may give you a quest to retrieve the Hydroelectric Magnetosphere Regulator from the reactor in Gecko to gain citizenship.
• If this quest is not available, having 120% Repair, First Aid, Doctor or 100% Science skill at 150% will gain you access.

Before joining Vault City, a good thing would be to collect rent for the guard, a quest that is not available to citizens.

Rewards

• Joining the Vault City faction (Access to the inner city and Vault 8). You are now a Vault City citizen !