What should I check before buying a used MacBook Air?

Check the battery cycle count (under 500 is ideal, under 1,000 is fine) and test every key on the keyboard—especially the space bar. On Apple Silicon models, the battery is glued in and costs $150–$250 to replace. Avoid 2018–2019 Intel models with butterfly keyboards, which are prone to sticky keys. Also inspect the screen for “staingate” (coating peeling near the webcam). If those three things check out, a used MacBook Air is a solid buy.