When buying a car for the 1st time will i need a co signer im 19 n if so why?

Often, if you're only 19, and will be making car payments, meaning you have financed the car, they will require a co-signer. You haven't been making payments in your life long enough to build up credit yet, so the bank wants a guarantee that if you stop making the payments, there is someone else they can get the money from. A co-signer is guaranteeing that if you stop making payments, they will be responsible for either forcing you to make the payments, or making the payments themselves. Either way, the bank gets their money.