To state the obvious, footing 100% of the bill to keep a roof over your head, the lights on, the fridge stocked and the hot water heater in good repair will be higher than splitting the cost with a partner. That assumes you and your partner aren't trading up to a home and lifestyle that is more than twice as expensive as how you live now.

The same goes for making a down payment on a home, as well as buying furniture, appliances and housewares. Beyond splitting such costs, couples who choose to get married have another advantage: They often get a financial assist by way of cash and gifts from their wedding guests.

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If you're single and lose your job, you lose 100% of your earned income. If you're living with a spouse or partner who also works, you only lose part of your household income.