Americans are marrying later or not at all, and more are cohabiting. The median age for first marriages is now 27 for women and 29 for men, compared with 20 for women and 23 for men in 1960, according to Pew Research. And about a quarter of those who have never married are living with a partner. Given those stats and the growing rate of divorce among those 50 and older, it’s important for couples to organize their finances and avoid fighting about money.

In the new book “Loving in the Grown Zone,” Zara D. Green and Alfred A. Edmond, Jr., co-principals of A2Z Personal Growth Enterprises, list some major money-related mistakes unmarried adults in romantic relationships should never make for love. That chapter’s title: “Stop Financial Foolery in the Name of Love.”

Here are seven mistakes for your cohabiting clients to avoid:

Don’t lend money casually

1. Don’t lend money casually without a written agreement that lays out repayment terms. Otherwise you may never get the money back. You will have no way to prove the funds were a loan, not a gift. 

Never co-sign a loan

2. Never co-sign a loan. Three out of four times, you, not the borrower, will end up repaying the loan. If you can’t afford it, your credit rating will be tarnished, not theirs.

Don't bust your budget to bankroll a lavish lifestyle

3. Don’t bust your budget to bankroll a lavish lifestyle for a significant other. 

Never assume financial responsibility for an adult dependent

4. Never assume financial responsibility for an adult dependent. Don’t pay the mortgage, rent utilities or other bills of a healthy, able-bodied adult. You have your own financial obligations to meet.

Never give your PIN, bank account numbers, ATM passwords

5. Never give your PIN, bank account numbers, ATM passwords or other personal financial information to a love interest. (I’d add Social Security numbers to the list.) Such broad access should be reserved for married couples.

Don't assume you can change someone’s financial habits and behaviors

6. Don’t assume you can change someone’s financial habits and behaviors, like a shopping addiction, credit card overuse and frequent late bill payments. “A person who engaged in financial infidelity when you met will not miraculously become trustworthy,” the book says.

Don’t be ignorant about your partner’s financial history

7. Don’t be ignorant about your partner’s financial history. Know it and treat it seriously. “Commingling your finances without knowing one another’s financial (including credit) histories is like having unprotected sex without knowing one another’s HIV status,” the book says.

Bottom line: No matter how in love you are, protect yourself at all times.

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