Buying a car
It may be a great idea, if you plan to take it back home, especially in Europe (see in bureaucracy section, you can save 30+ thousand dollars on tariffs/tax/price, depending on a model- from previous experience, you can save a lot on some Jeep, Subaru, Mazda, and Nissan models). Always negotiate the price for a new car, relying on info from websites such as CarsDirect. Dariusz did it twice, always was at least able to meet the price from CarsDirect.
If you buy a used car (which Dariusz did once, but you should be aware it is a snake pit), definitely invest into CarFax (a website listing all major accidents for a car, basing on its VIN number), and also check Kelley Blue Book to estimate the used car actual value. Whether you buy a car, or just rent, AAA membership is good in case things go wrong on the road and quite cheap.