Used treamills recently became very popular since leading brand treadmills aren't cheap, but many customers are unaware of the major risks involved when buying a used treadmill. You get zero warranty and while you can be lucky to get a good deal, you may end up with a broken or malfunctional treadmill as well.
Best advice for consumers is the look for new treadmills on sale or special discounts e.g. available on the reputable http://www.buytreadmillsonsale.com website. You will save alot compared to the regular and official price, but get a full warranty, free shipping right to your home and all the advantages of a completely new treadmill. The price is only slightly higher compared to used treadmills, but without any security or warranty risks.