There is nothing wrong with second hand bikes but if you want to buy, you should check profile of seller.Now a days there are most of the cases in which bikes are stolen and then sold, so we should aware of this that the bike is safe or not.now after that bikes so before buying second hand bike please do not check how bike is looking from outside but check the interior part like engine, tyres and rest of the things.if bike is good from inside it’s green signal for you.exterior part we can modify in less amount.so this type of thing you should check before buying a good second hand bike.