What is a decent down payment for a $25,000 car?

Okay so My dream car is a 2017 Honda Civic si. I've always wanted a si since high school. I'm 20 years old with no credit but my grandpa as always told me if I wanted that car then I need to come up with $2500 and he will let me cosine with him (he has perfect credit). I don't know about you guys but don't you think I need a little more than $2500 since the car is $25,000? And plus I don't want my payments to be like $600 a month, the maximum payment a month I would prefer is $300 but nothing above that. I don't want the car until next summer anyways so I have plenty of time to save up so what do you guys think is a good down payment for that car?

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