There are good and bad points about buying on eBay, but it's important to understand the risks.
Buying from unknown sellers here isn't like buying from the shops. The user agreement even warns buyers that "eBay does not guarantee the existence, quality, safety or legality of items advertised, or the truth or accuracy of descriptions".
eBay provides it's own money back guarantee or most items, but it only lasts for 30 days. After that, eBay has no interest - it's between you and the seller. Many sellers don't want to know, and even manufacturers' warranties are often invalid for items bought here. eBay is a jungle.