Not knowing anything else about the vehicle (such as price), I would not choose to buy a 15-year-old car with 225,000 miles on the odometer, unless the previous owner can show you service records indicating proper and regular maintenance. You might want to check to see what other used cars are available within the same budget.
Did you know that you can find used car values at the AskPatty Car Buying Service? http://www.askpatty.com/click.php?ID=367
Powered by ClearBook, all you have to do is enter your year, make and model, and answer a few questions about the condition of your vehicle, and you'll find fair market values for your used car.
Please take a look, and let us know how it works for you!!