No, that does NOT sound right! If you have any questions at all as to whether or not this is a good purchase for you, rescind immediately! The deal will still be there once you've had time to research it. But, once those five days pass you'll own it whether it's good for you or not.
$15,000 is a lot of money. Would you spend it that fast on any other kind of purchase without doing some research?
Be sure to follow exactly the rescission instructions in your contract. Send your letter by certified mail so that you'll have a receipt from the post office to prove that you sent it in time. Don't talk to the sales staff any more about it.