Over the years I have purchased quite a few used and refurbished laptops and other types of computers through eBay. I have had almost all good experiences, but you really have to do your research on both the seller and the computer.
This has been some 20+ years ago in the mid stages of the internet buildup. My young gun boss bought some switching equipment from a 3rd party resale outlet like Ebay. The university IT guys came in for an audit and they determined the equipment was still registered to a major defense contractor. It wasn’t long after that the university central IT department seized control purchasing and control of networking equipment.
Yes you must research your eBay seller. Dell outlet- refurnished was very good for laptops in 2020-22. I looked last week and not so good. Check out VipOutlet... they are kinda the reseller for Walmart. Both are in Arkansas. VIP also sells via eBay and Walmart.com, with different prices for an item than the Vip website. I have bought from Vip and Dell refurbished. Ebay used too.