Plenty. A used car is always more valuable to the owner if you can sell it personally. There are a few "blue books" and it depends upon which one your dealer uses. Plus, many dealers make up what they lose on the sale of a new car, by what they don't give on the trade in value of the used car

The offers come from the main office/factory, not the dealership. So unless they post that not everyone qualifies for the 0%, they have to give it to you. Often the price of the car is higher if you go with 0%. Cash deals are always better. Even if you can't afford to do that, check with your bank first, give them all the details on the car you want to buy (leather, sun roof etc) and let them tell you what they would loan you to buy that car. If you can do that, it's cheaper anyway usually. But at least you will have the honest value of the new car that way.

Don't trust anything the salesman says.
Have all the paperwork in writing ahead of time to read.
Don't walk in and buy the car. get info and leave! This is hard, but you are less likely to get taken on every detail this way.

check with the better business bureau for what type of complaints are filed against the dealer.

Good wishes!