Social Security serves as a critical source of income for many retired Americans. But one of the biggest myths surrounding the program is that everyone is entitled to a monthly benefit once they reach a certain age.

In reality, Social Security benefits have to be earned. You can set yourself up for benefits in retirement by accruing a total of 40 work credits in the course of your career.

The value of a work credit can change from one year to the next. Right now, for example, it takes $1,640 in earnings to qualify for a work credit. Next year, that threshold is rising to $1,730. But because you can only accrue up to four work credits per year, generally speaking, you can qualify for Social Security benefits by working at least part-time for at least a decade.

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But what if you never worked for money a day in your life? Maybe you've always had an unpaid job, like raising children and being a caregiver. In that case, you might assume that you won't be entitled to Social Security. But you may, in fact, be eligible for benefits depending on your marital status.

You may be entitled to spousal benefits

If you're married to someone who's eligible for Social Security, or you were married to someone in that boat for 10 years or longer but are now divorced, then you may be eligible for spousal benefits. Those benefits can equal up to 50% of what your current or former spouse collects.

If you're married, you'll need to wait until your spouse files for Social Security to start receiving spousal benefits. If you're divorced for two years or more, then you can claim spousal benefits before your ex-spouse files.

Your spousal benefits won't affect or take away from the benefits your current or former spouse receives. Rather, the money you're entitled to is separate.

You may be eligible for survivors benefits

If your spouse has passed away after being eligible for Social Security, then you may be entitled to survivors benefits. Unlike spousal benefits, which max out at 50% of what your spouse is eligible for, with survivors benefits, you could be in line for up to 100% of the monthly benefit your spouse collected.

You can also start out collecting spousal benefits and then have your payments bumped up if your spouse passes away. Let's say you have a spouse who's eligible for $2,500 a month from Social Security. You might file for spousal benefits and get $1,250 a month yourself. That number might then get increased to $2,500 once your spouse passes.

Know the rules

Clearly, it's more than possible to receive benefits from Social Security without having worked. If that's the boat you're in, read up on how spousal and survivors benefits work so you know exactly what to expect.

It's also good to have that information because it might affect your spouse's filing decision. If your spouse signs up for Social Security early, for example, it could leave them with a lower monthly benefit. In turn, that could leave you with less income from Social Security. That's the sort of thing you'll want to talk through together.