People are often worried about the car buying process partly because they are unsure how much they should expect to pay monthly.  If you finance, your payment is is a function of 3 things: (1) the amount you borrow, (2) how long you borrow it; and (3) how much interest you agree to pay.

Assuming you borrow $10,000 at 7% for 60 months you will have a payment of approximately $200 a month.  Put another way, you are paying $20 for every $1,000.  So if you were borrowing $20,000 at 7% for 60 months your payment would be twice as much or $400 per month.

More experienced shoppers will recognize this example and put it in terms of a factor - .020.  So if you multiply the amount of money you are borrowing by .020 it will give you your payment (assuming 60 months and 7% interest).

So before you go shopping for a vehicle - figure out what the monthly payment should be by clicking here on a finance calculator.

http://www.edmunds.com/apps/calc/CalculatorController?mktcat=new-fiw-auto-finance-calculator&kw=finance+calculator&mktid=ga44333273&gclid=CIeEkrG-hpQCFRcZsgod0ifjWA

Now if you have credit issues, typically your payment will be $250 for $10,000 borrowed or $25 for every $1,000; or a factor of .025. 

What if you lease? Well similar rules of thumb can apply. A lease is typically $150 per month for every $10,000 worth of vehicle. So if you are looking at a $20,000 vehicle and leasing for 36 months with no money down, you should have a lease payment of $300 (plus sales tax and registration fees).  Put in terms of a factor - a lease is a .015.