Undercarriage Condition: Track pads, rollers, and sprockets should have even wear. Replacing undercarriage parts can cost $15k+.

Fluid Analysis: Request oil/hydraulic fluid test results to detect contamination or metal particles.

Technology Compatibility: Newer models (e.g., Cat 340) may include GPS/telematics. Ensure older units meet your tech needs.

Operator Feedback: Research common complaints for specific models (e.g., hydraulic leaks in older 330s).

Dealer Support: Choose sellers providing post-purchase servicing or troubleshooting guides.