5 Money Mistakes Made in the Name of Love

"I don't know if it's ever really good to combine credit," he said. "I think it's a natural tendency that couples want to do it as part of the process of bringing themselves closer together. But I think that couples must always maintain separate credit files because death, illness or divorce requires that each member of the couple be able to stand on his or her own feet."

"So often the boyfriend or the girlfriend with the bad credit will say, 'Please, let's get a credit card together, it will help me build my credit and you would be so wonderful if you would do this with me,'" Cunningham says. "Don't do it. There is joint control of that credit card which means you may very desperately want him or her off the card, but your hands are tied if they won't budge. If somebody turns into a jerk, they can run up your credit, refuse to pay and nobody can force them to pay. They are off scot-free."

As an alternative, she suggests making that partner an authorized user of an existing credit card.

"Then you can kick that person off whenever you want to and you've remained in control of the card," she says.

Dragging in family members
If it isn't advisable for one half of a couple to get tied into the other's loans and bills, it is even more dangerous to bring family members into the picture. No matter how well a partner gets along with the potential in-laws, introducing money to the equation is an invitation for trouble.