The nomads' economy is, on one level, simple. Households raise sheep, goats, and yak under a "natural" system of pastoral production. Their livestock are not fed any specially sown fodder plants or grains, and survive exclusively by grazing on range forage.
This can be very tricky however, because if they were to settle somewhere with higher altitude, that would pose a problem, as there would be a very short growing season. I hope this helps!