I think that rent, utilities, and car/insurance payments should add up to about half of what i make every month (with the other half being for savings, food, gas, stuff, speeding tickets, et cetera). So how much i need saved before buying that car would depend on what i make and also the rest of my living situation.

I recently bought my car, and to total out to almost exactly half my monthly salary, i could afford an $80 payment. So i saved until i could put enough down to get the payment that low. But i agree that it doesn't make a whole lot of sense to pay interest on a car. My only reason for financing this was an effort to build a credit score, as i went into it with absolutely none.