Buying used treadmills can be a risky business and unless you do your home work you will probably buy yourself a white elephant. While most people just look at the cosmetic aspects of a second hand treadmill, the real problems are rarely cosmetic. In fact, many machines that look shot are probably still perfectly fine and can be still be used for years to come.The main differences in price tags is not the features or the latest and greatest gadgets. it really comes down to the core components of the treadmill that really determines the way it performs. Lets quickly look at the 3 most important things you need to look out for before you buy a used treadmill.1. The MotorThe drive motor is at the heart of the machine and it is the most important thing to look out for. As a rule of thumb, any machine with a motor that has a capacity of less than 1.5 horsepower (CD) won't last and most used treadmills with small engines are probably worthless.2. The Drive BeltThe belt forms the running surface and is subject to a lot of wear and tear. Once the belt starts tearing and threading its inevitable that it will need to be replaced. The smallest tear can start opening up and once this happens it can start damaging the motor. Check the belt carefully and if there are any tears in it (especially at the sides) its no good any more.3. The FrameTreadmills are subject to a lot of corrosion and with sweat dripping on the frame, it can become corroded. Once the frame starts corroding it will just keep going and eventually go straight through. Aluminum frames don't corrode and if you spot any corrosion then its probably a steel frame which is cheaper and a lot less robust. It is heavy though which makes, generally speaking, for a more stable treadmill.Are you looking for quality used exercise equipment? See my blog and learn more about buying used treadmills.