If you decide to buy a used bike online, it's important to consider what kind of warranty is offered with your purchase. Many times it is the case that an online retailer will offer a return policy but not a warranty. This is why reputation is so important and why reviews matter. Check out The Pro's Closet for Certified Pre-Owned
For stores that do offer warranties on used bikes, there are often two main types of warranties. The first is the manufacturer’s warranty which is usually included with the purchase of a new bike and could still potential be in effect for a limited time. This warranty will cover any damage to the bike during shipping, manufacturing defects, and any other problems that may arise.
The second type is the store’s warranty which only covers damage to the bike during shipping and manufacturing defects. These are more rare but do exist.