i want to buy a used audi

These are great cars, better in many ways that the later A4's. The B5 chassis is more compact, lighter and responds well to tuning and modifications (if that would be the intent) very well. Just make sure the timing belt has been done, or at least do that right away. However, it is impossible to tell you if it is "worth it" if you don't state how much you are willing to pay for it.

sorry about that but its going for 5,998$

Not a bad price. Not a great deal either. I got my '03 with 83K miles for $9,900. It's in perfect shape. Totally up to you. I think your car has another 100K in it and I love my audi. I'd buy it if I were in your shoes.