When shopping for a used airplane, hire a mechanic to perform a careful inspection, and then carefully review logbooks and other records for possible major repairs. It is also advisable to personally fly a plane before purchasing it.
Ask a mechanic to perform differential compression checks on each engine cylinder. Take the time to find out whether or not it is possible to purchase spare parts for the particular plane in the event it needs repairs. Older planes that are no longer in production are sometimes difficult to find parts for, as are handcrafted airplanes. Many mechanics refuse to work on either of the above in part owing to liability worries.
To be sure there are no liens against the aircraft, pay a nominal fee to have an aircraft title search conducted through Aircraft Title and Escrow Service.
While flying an airplane you are considering buying, carefully check all systems, instruments and equipment to ensure everything is in good working order.
Finally, sign a sales contract including terms and conditions of the purchase agreement in writing. While such a contract need not be complex, it should clearly outline the intentions of buyer and seller. Many attorneys are willing to prepare such contracts for a flat fee.