I am guessing you didn't mean you want a brand new car just for $4000 (although your post sounds like that's what it means). If you meant you want a new car and are willing to put $4k down, then that's a different thing.

If your budget is limited, I suggest not to get a brand new car. Yes, you will get financing but the terms will be ridiculous - your monthly payment will be too high. Remember, you have to pay for tag and registration so keep aside a grand for that. Then go get a reliable second hand.