The first and most important step in choosing a used woodworking machine is to decide which machines you will need to begin with. Several options exist for woodworkers, and it will be important for you to consider both the function and size of the used woodworking machine before purchasing. If you are short on space in your workshop, you may want to consider a combination machine, though if you will be performing jobs every day in a professional capacity, individual machines may work best. Regardless of which machines you need, it will be important to perform a visual inspection and test out the machine in a real working situation.
The specific criteria for choosing a used woodworking machine will vary according to what kind of machine is being purchased. If, for example, you intend to buy a table saw, you will need to inspect different components and look for different signs of wear than if you were to buy a planer or thicknesser. The best way to be prepared for an inspection of a used woodworking machine is to learn as much as possible about the function of the machine as well as the common issues a specific brand or model may have. An Internet search should reveal any recalls or common problems to look for.
Consider buying a used woodworking machine from a dealer rather than a private seller. You will probably end up paying more when you buy from a dealer, but you may also be able to get a return policy or even a warranty from the dealer, whereas these are highly unlikely coming from a private seller. If you research the common selling price of such machines ahead of time, you will have a good understanding as to whether the seller is offering a fair price; the more educated you are about a particular machine, the less likely you will be to be cheated or ripped off.
Remember that, despite a thorough visual inspection and test run, the used woodworking machine may be worn in ways that are not visible, meaning it may break down after you purchase it. Whenever possible, get a warranty or return policy from the seller, and be prepared to pay for repairs or parts replacements shortly after purchase. It helps to budget such money ahead of time and set it aside should a problem arise. Consider whether the machine is up to date so you will be able to purchase replacement parts if necessary. Unless the price is unbeatable, avoid machines from manufacturers that no longer exist, as you will not be able to get replacement parts in most situations.