I'm going tonight to turn in my leased vehicle and buy a new truck. I've done my research online, but how do you know you are getting the best deal? I was once told that if you pay more than $500 over invoice, you've paid too much. Can you ask to see their invoice? Is there a general rule of thumb that you can usually go so much below what they offer initially? I'm looking at the Ford Rangers and F150s in case that matters.