Large down payment for a corvette c6?

[XBOX360GAMER]

I was going to save up 20,000 and try to buy a corvette c6 2005 from a dealer it sales for 25,986 and has around 38,000 miles what are the up and downs and gta tony im sure your going to read this it's not going to be soon I make 450 a week and bring home about 1800 home a month but I don't plan on getting it in till I have 20,000 is that bad I heard large down payment = better payments and I check and a insurance for a 18 year old in a corvette would be a little high but if I put a large down payments the notes would be cheap around 300-500 THE QUESTION IS AM I CORRECT ABOUT LARGE DOWN PAYMENT