Do a Delivery for a Gecko Express
Gecko Express is a network of post offices in post nuclear war California. They have their branch offices in Boneyard, Shady Sands, Vault City and San Francisco Caravan Depot. If you want you can work for them - they are paying in solid caps for every succesful delivering.
Doing Deliveries is the only way to gain Pathfinder perk. You will receive this achievement after 15 successful deliveries.
Here are their locations:
Depending on the course you will get different amount of caps. Here's the full list.
San Francisco to Boneyard: 150 caps.
San Francisco to NRC: 150 caps.
San Francisco to Vault City: 150 caps.
Adytum to Vault City: 200 caps.
Adytum to NRC: 75 caps.
Adytum to San Francisco: 150 caps.
Vault City to Adytum: 200 caps.
Vault City to San Francisco: 150 caps.
Vault City to NCR: 120 caps.
NCR to Vault City: 120 caps.
NCR to San Francisco: 150 caps.
NCR to Boneyard: 75 caps.
If you ever find an courier package and decide to return it to one of offices you will get 50 caps.
Note: This quest is usually done for obtaining very useful achievement called Pathfinder. As we wrote earlier you need to do it 15 times before you will receive it.