Prenuptial agreements aren't just wise for people who are going into a marriage with significant assets, a business, anticipated inheritance or children from another relationship. They're a prudent measure for just about any couple getting married. They can help define which assets and debts are to be considered yours alone -- not just those that you bring into the marriage, but those acquired later. In legal terms, separate property generally applies to property you had before you were married and anything that you alone inherit after marriage.

Some people balk at the idea of a prenup because they see it as cynically "planning for divorce." As one certified financial planner notes, however, "It's cynical to put on a seat belt when you pull out of your garage, because you're planning for an accident ... You want to be safe if that happens, God forbid."

A Prenup Alone Doesn't Keep Separate Property Separate

A prenup is an important first step to detailing separate property. However, you need to keep this property separate. Once these assets are commingled with marital ones, they're no longer separate, and are potentially subject to division in a divorce.

A common way that people inadvertently commingle separate property is by putting inherited funds into a joint account. Another often involves real estate. If you use money from a joint account to make renovations or pay taxes on a home that's only in one of your names, that home can be considered marital property. Remember, too, that if you purchase a boat or a valuable piece of art with funds from a joint checking account or credit card, it's not separate property.

Why Separate Accounts Are Wise

Many family law attorneys recommend that couples keep some of their money separate, whether they have a prenup or not. While a joint bank account and credit card are probably necessary for household purchases, family vacations and children's expenses, it's smart for spouses to have some accounts in their own names.

These separate accounts can be useful if you receive an inheritance or gift, or if you want to make purchases that are yours alone. They can also provide some financial protection if your spouse suddenly leaves or lands in serious debt. Creditors can go after joint accounts, but not ones that the debtor's spouse holds alone. Separate accounts can also make inheritance easier for children you had before your current marriage if you die before your spouse.

While working on your prenuptial agreement, your family law attorney can provide additional guidance on how to avoid commingling. Once you understand what commingling involves, it's easier to avoid accidentally doing it.