Guard the caravans

The Hub offers many employment opportunities for the resourceful wastelander and one of them is a semi-permanent job as a water caravan guard. There are three companies that hire additional guards and each have different routes and varying difficulty. The one common requirement is that you bring your own ammo, armor and guns. Upon arriving you have about an hour to have a look around, after that the caravan leaves and heads back home.

Abandoning the caravan (i.e. running to the exit grid before all hostiles have been slaughtered) will prevent you from taking any further jobs with that company, as will insulting their boss, stealing from them or killing the caravan yourself (obviously).

Crimson Caravan
By many regarded as crazy, the CC offers the greatest variety of caravan routes to work on: Junktown, Boneyard, Necropolis and Brotherhood of Steel. Their encounters are also the hardest and require good weapons and armour to make it to your destination, not to mention, you are guaranteed to have one. The pay is 600 Hub bucks each way, making for a total of 1200 caps both ways.

They only leave twice a month, on the 3rd and 17th. To get on a route, talk to Keri in their downtown office, after getting the all clear from her father, Demetre.

Far Go Traders
Commonly regarded as the nicest merchant company in the Hub, the Traders offer good pay (400 scripts each way), have moderately difficult encounters (and a 75% chance to even have one) and work the routes to Junktown, Boneyard and the Brotherhood of Steel. They leave thrice a month, on the 8th, 18th and 28th.

Talk to Rutger and then to the caravan driver in their building to hook up with a caravan.

Water Merchants
The biggest company in the Hub is also the least profitable, at least to guards. They only work two locations, Junktown and Adytum, and offer 200 bucks each way. However, you are least likely to get an encounter on the way (5 in 10 times) and they leave most often (1st, 5th, 10th, 15th, 20th and 25th).