So, he offers the driver a bonus of 60 centavos for every head of cattle that arrives in good shape. The journey is dangerous for the cattle. They can drown, they can fall prey to disease or predators, they can be stolen by bandits, or they can just wander off. The rancher knows that even the best driver is almost certain to lose at least five head, so he offers the driver an extra five cattle to take along. So, the driver is really transporting 1,005, and not 1,000.
Cattle vary in quality, and it's important to have good, strong ones in the lead.
The driver's pay is partly based on the condition of the cattle upon arrival, so he won't want to be handed the worst specimens that the rancher can find. So, the rancher allows the driver to pick the first 100 head of the 1005 to be driven. Knowing that checks aren't universally accepted in the wilds of Mexico, he also provides some silver and cash. The rancher is much better situated to provide up-front money than the driver is, so he provides the capital needed to get the operation going. In addition to the money for unforeseen expenses and some money for routine expenses, he provides a horse, saddle, and equipment.