Questions before buying a used Phaeton

Dear forum, I am currently playing with the idea of buying a Phaeton. Originally I had planned an amount of up to 20,000 EUR for it. But now a dealer recommended me to choose the 1% financing, also my tax advisor finds the idea great. What is the right one for me I still have to think about. So much for the background. The catch is, the 1% financing only takes place from 30,000 EUR. But for this you get cars with guarantee, or can conclude a guarantee for it. Now I ask myself of course if you have to buy this at all, since I still can’t say how much and if the Phaetons still cause problems. I would like to hear what you have done for experience, whether it is better to buy one from 2008 for little money but without guarantee or to buy a newer one from 2011 with guarantee. Maybe if you also have a few tips for a newcomer I would be very grateful. I have already read every amount but can not channel all this yet so properly. Many thanks and many greetings.