What is the catch with 0 percent financing?

When dealing with a vehicle loan, sometimes they raise the total cost of the vehicle so your down payment doesn't count by adding it into the fees. However, you do have to pay taxes and smog/license fees. Its hard to tell if you're getting a good deal past asking, "Is it worth it to purchase this at this price?" You look at the market and ask yourself if you went somewhere else, would you get the same product at a better price? Sometimes businesses offer 0 percent financing as an incentive for more customers to buy their product(s). However, 0 percent financing is usually OAC (On Approved Credit). You'll get financed at 0 percent if your credit meets a set minimum criteria.