You receive a credit card offer through the mail. It says that you can borrow up to $2000 at 18% interest per annum and pay as low as $40 per month. It sounds like an excellent deal and the monthly payment on most credit cards is usually calculated at around 2%. At 18% interest, you’ll be paying $30 as interest and $10 towards principal. At this rate of $40 a month, you’ll take 30 years to pay the principal and interest. Think again! You cannot afford this kind of credit card. You need to chase a credit card that charges a low interest rate.