Buyers must prioritize the engine model and hydraulic pump condition, as these are the core components of Hitachi machines (e.g., Isuzu engines in many models). Check the operating hours; typically, a machine with under 5,000 to 8,000 hours is considered to have significant remaining service life. Inspect the undercarriage wear (track links, rollers, and idlers), ensuring it has at least 60-70% life remaining to avoid immediate maintenance costs. Additionally, verify the bucket capacity and boom/arm integrity for any signs of re-welding or structural stress.