Brahmin Run for Martin
Once you get inside the Westin ranch in Shady Sands, you can talk with Martin to get jobs running herds of brahmin to nearby farms in the wasteland. You can opt to run the cattle to a closer farm or to a more distant farm, getting paid more per surviving brahmin if delivered to more distant farms.
Note: This is a repeatable job and creates a temporary location on your map which should not be used to store gear.
You can enter dialogue with Martin and accept the job empty-handed and you'll have an opportunity at the end of the dialogue to go get ready, but once you start the quest you'll be on the map over NCR with nobody in your party list. That's okay - just find the destination on the map and go there. When you get interrupted with forced encounters, there you will see the herdsman and the cattle. They don't fight even when attacked, so you have to do all the work.
Continue to the farm (again with nobody showing in your party list) to deliver the brahmin. Then head back to Shady Sands and talk with Martin again to complete this job.