7 Net-worth killers

Certified financial planner Mari Adam has seen couples with car payments totaling $1,400 a month. Would it kill them, she wonders, to drive cars that combined would cost them closer to $800 or $900?

Another planner, Chris Cooper, has suggested as a rule of thumb that you don't spend more than 8 percent of your monthly gross income on a car payment, less if you have credit card debt.

Money Magazine has estimated that driving less expensive cars could yield an additional $180,000 over 30 years, assuming you invest your savings.

Remember, in addition to your monthly payments, you'll be paying for insurance, fuel, maintenance and repairs.

To find out a car's cost of ownership over five years, use Edmunds.com's True Cost to Own calculator or Intellichoice's Side-by-side Comparison.