Buyers must prioritize the engine hours (working hours), as this is the primary indicator of remaining service life. For tractors, verify the Horsepower (HP) rating and PTO (Power Take-Off) functionality. For harvesters, inspect the threshing system and grain tank capacity. Always request the original engine brand (e.g., Cummins, Perkins, or Yuchai) and ensure the hydraulic system shows no signs of leakage or pressure loss. It is recommended to choose machinery with less than 3,000 working hours for optimal ROI.