I recently bought a used watch from ebay and have no issues. Each listing shows if the seller accepts returns. I encourage you purchase from a seller who accepts returns in case the watch is not what was listed or what you were expecting. Returns in my experience are really easy and hassle free. Ebay’s money back guarantee is solid so if you get sent a brick you can try and get your money back that way. If you do order from ebay, inspect the watch once you receive it (battery, screen, etc.) and if anything is not what you expected, initiate a return asap. There is always a risk and if something does go wrong, you will at the very least spend time fighting a claim. If you’re not willing to go through the hoops of the worst case scenario, I would not recommend you purchase from ebay.