For online car loans, how much should I apply for if I don't know the cost of my car yet?
How do I pay the car dealer when I finance my auto loan with an online lender?

It's very simple! You have not decided whether you want the Toyota Camry or Honda Accord, but you do know the sticker prices of these cars. So while you are car shopping go ahead and apply for your auto loan online. For example if your car has a sticker price of $25,000, you just apply for your car loan seeking $25,000 plus tax. The online car loan lenders approve you up to that amount, and FedEx you a blank check which you are authorized to fill out at the car dealer up to your approved amount. Whatever amount you write in that blank check becomes your car loan amount, usually a number much less than you applied for. So you see, it does not matter what the final selling price of the car is, it will likely be less than your car loan approval amount. So haggle your best deal at the car dealer, and with your down payment, you'll be way below your pre-approved auto loan amount. This allows you to secure your auto financing a month before you buy your car, then you just endorse the check over to the dealer when you buy your car. Bottom line is you do not need to know the final cost of your car when applying for your car loan, so apply now at sites like Capital One Auto Finance and HSBC Auto Finance. You need to be pre-approved for auto financing before you ever talk to a car dealer to avoid scams and get the lowest APR.