Check the Battery Health percentage in the settings. Anything below 80% will likely require a replacement soon, which should be factored into the negotiation.
Platforms like eBay, Facebook Marketplace, or Swappa offer the lowest prices. Swappa is particularly noted for its verification process, which prevents the sale of blacklisted or stolen devices. However, buying from an individual requires the most due diligence. The Essential Checklist buy second hand iphone
The "where" is just as important as the "what." Buyers generally choose between two paths: Check the Battery Health percentage in the settings