When it comes to these money “rules,” following conventional wisdom can cost you.

Conventional wisdom is often a good thing, or at least harmless. For instance, even if chicken soup doesn’t help your cold – and research shows it probably does help – it won’t hurt you. Plus, you’ll help keep someone employed in the soup industry.

But there are plenty of times when conventional wisdom isn’t just wrong – it can cost you money. So the next time you’re about to make a big financial decision, keep in mind that rarely is anything black and white when it comes to the green stuff. Here are five money rules that are largely wrong.

Carrying a credit card balance will help your credit score. Not at all. If you are carrying a balance you can’t pay off, it will help to keep the balance as low as possible because credit bureaus don’t like to see a high debt-to-income ratio. In other words, they want to see that you aren’t maxed out to the limit every month. So intentionally carrying a balance on your card won’t put your credit in better standing or save you money; paying interest only benefits the credit card companies.

Having a zero balance every month on your credit card is fine, especially if you’re making regular or occasional purchases and paying them off monthly. Credit bureaus like to see that people are using credit cards responsibly. That’s why never using a credit card that has a zero balance won’t appreciably help your credit score, either.

Pay off credit card debt before saving for retirement. Ultimately, it comes down to how much debt you’re talking about, and what kind.

One myth that young professionals – actually, many professionals – initially question is whether they should pay off consumer debt, like credit cards and student loans, before fully investing in their company’s 401(k) plan, says John Oxford, director of external affairs at Renasant, a financial services company headquartered in Tupelo, Miss.

What’s so wrong with paying off the massive credit card debt you accumulated in your early 20s before sinking money into a 401(k) plan? Oxford says if your company offers a 401(k) contribution match, and you instead shovel money into debt, you’ll pass up on what amounts to free money that could have gone toward your retirement.

You’re also losing out on the potential interest growth, he says.

So, yes, save for retirement at the same time, even if that means it will take longer to pay off your debt.

Stocks make you rich – and bonds keep you rich. A good rule of thumb, but this is another gray area.

The bond bull market for the past 30 years is coming to an end, says Jon Ulin, a managing principal at Ulin & Co. Wealth Management, a branch of LPL Financial in Boca Raton, Fla. Interest rates will begin to rise when the Fed starts to taper the monetary stimulus program. Bonds tend to fall in value when interest rates rise. As [when] there is a greater degree of price volatility for longer bond maturities, investors should move more into short-duration bond investments.

Benjamin Sullivan, a certified financial planner with Palisades Hudson Financial Group in Scarsdale, N.Y. echoes that thought.

He says it’s a myth that retirees should be fully invested in bonds. Even retirees may have a relatively long time horizon for a portion of their money, he says. They need the superior growth that stocks can provide to retain purchasing power over their life.

Home additions increase your home sale value. Usually they don’t, says Patrick Roberts, a certified financial planner and CEO of PKR Investments in St. Louis. If you add on a room or an amenity like a swimming pool for the sole purpose of adding value to your home, he says, you’re likely to hurt your pocketbook. That’s because even if your addition does add value to the house, you’ve likely taken on more debt in the process, so you may lose money in the long run.

Now, if your house needs a fresh coat of paint, feel free to slather it on. You will probably sell it faster and maybe for a bit more. But when it comes to high-priced add-ons and features, proceed cautiously if your only goal is to add value to your home.