they usually add the price of the payoff to the new loan, resulting in a larger loan

Not necessarily. The average car owner trades their vehicle in every three years and usually stays right in line with the amount of monthly payments unless you got way upside down with your last car purchase.

Bad move. You are financing and old loan, so your payments will be higher. This also makes you paying longer on your original loan.

You will have to pay for the new car plus what ever they paid to pay off your other loan.

not sure what you're asking - higher salary for yourself or a higher interest rate or a higher payment
salary should be given by you only - don't let the banker chane it
interest rate will depend on nat'l rates a the time and your credit and the length of the loan compared to the car
payment will depend on the amount financed, the interest rate, and the term.
Your credit will be the biggest determining factor in if you can buy a car. They'll check how high your debt is compared to your income. But so many people end up paying much more b/c they have moderate or low credit.

the previous answers talked about having to pay off the balance of the initial loan. that is usually negotiated in the 2nd car deal b/c the dealer has to find out what is owed anyway. So yes that amount (if upside down) is added to the price of the new car but the package is usually brought out to you w/ that figured in.

it depends on how much trade in value they gave u on the old car compared to how much was still owed on it and how much at what apr is financed on the new one. my guess is yes the payment is going to be larger but if you want nice things you have to pay the price!

in my experience, the only way to go down is to decide to go down in type of car. Ask yourself - can I accept less car if the payment is less?!