BEFORE YOU DO IT... Guidelines to consider

If marriage is important to you, ask if he shares that goal. If you're hesitant to pose the question, that's a bad sign, Spio said. "A lot of women don't ask because they'd rather not find out."
If you're willing to take the chance that he'll warm up to marriage, set a deadline and stick to it. Many women fall for lines such as "I haven't ruled it out" and "If I married anyone, it would be you," and allow themselves to be strung along for years, Wachs said. Two years is a reasonable cut-off, especially for women who want to bear children, Spio said. "If after two years he's still using 'I' instead of 'we,' chances are it's not going to go anywhere."
Don't move in too quickly. "You should be going out for more than a few months before you live together," Sacks said. "It should be taken a little more seriously than some people take it."
Draw up a "shacking-up contract" before you move in. Spell out such things as who owns what, how the money and property is divided and paid for, and who would keep the pets. Visit a lawyer or mediator to make it binding.
Keep your finances separate. "Women should resist the urge of getting a joint checking account with their love interest during the early stages of living together," Sacks said. "While part of you may feel that pooling your money is a gesture of togetherness, it's also a gesture of financial risk and should be avoided."
Live within your means. Try to sock away any gains you incur from sharing expenses to cover in case you're suddenly on your own again.
Discuss how you will divide household labor to limit surprises. Make clear your stance on domestic chores. "A lot of women aren't into cooking and cleaning like their mothers were," Sacks said.