making a living in the mountains
Refers to earning one's livelihood through mountain-based work such as forestry, hunting, or gathering.
彼は若い頃、山稼ぎで生計を立てていた。
When he was young, he made a living by working in the mountains.
Compound of 山 (yama, 'mountain') and 稼ぎ (kasegi, 'earning, work').