Searching online auction sites, such as eBay, is one way to buy a used Porsche Boxster. Other options are buying from local auctions, from classified ads on websites or in newspapers, or from a dealer or collector.
When buying a Boxster, compare prices and search through completed eBay listings for the same model and year of the Boxster you are considering. Find out the Kelley Blue Book value of the car.
Find out as much as you can about each individual car you're considering before making a purchase. Get a thorough service history to ascertain whether the car has been properly maintained. Find out if any warranty is left on the vehicle. If possible, have a mechanic give the car a thorough inspection. If buying online, check out the seller's sales history, and look for warning signs such as unsatisfied customers or complaints about misrepresentations in previous sales.
If you can assess the car yourself, look for doors or windows that don't seal properly and can cause leaks. Check the tires for signs of excessive wear, and test for play in the steering wheel. If you are buying online and can only look at the car in photos, look for a clean, polished car. Check out the quality of the upholstery, carpets and leather. All these can tell you how much care has gone into maintaining the car.