Mona started donating her eggs in 2012, not long after she arrived in the U.S. from the Middle East. As a refugee, Mona, who asked to keep her last name private, ran up credit card debt while she was securing her refugee status and wanted to repay it quickly. "I started to donate because I heard that there was good money," she says. "When I heard [I could make] between $6,000 and $8,000, I thought, 'Great, an easy way to make money, close out my debt and be comfortable.'"

Mona is now donating her eggs to a fertility clinic for the sixth time. She anticipates this donation to be her last and, for her, the temporary discomfort, pain and doctor's appointments are worth the payout. She notes, however, that egg donation is not for everyone. After all, "you are giving up children in the world," she says. "I don't know how it would be [for others] psychologically."

Submitting to medical research or donating your plasma, eggs, semen and other bodily materials may seem like an easy way to make money on the side. In fact, it can sound more palatable than grinding out inconsistent pay as a driver for a ride-hailing company, seasonal worker or gopher for a task-managing app. Plus, there's the altruistic side: Your donation may help a couple become parents or create a new miracle drug. You may save a life – or create one.

But medical donations require unique considerations, experts say. You'll typically need to be relatively healthy, you may need to be young and you'd better not have a fear of needles . Here's what to know about donating your plasma, eggs, sperm and other body materials for money.

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Selling Plasma

You won't get paid to donate blood to an organization such as the Red Cross, but selling your plasma can net profits. When undergoing the plasma-donation procedure, your blood is drawn, the plasma is separated out in a machine, and then your red blood cells, other blood components and some saline solution are returned to your body. Plasma is a portion of the blood that looks like light yellow liquid. Its job is to carry other components throughout the body. Plasma can be donated without reimbursement at a center like the Red Cross, but pharmaceutical companies will pay for your donation, which helps them create plasma-derived medications and treatments.

Because you're not donating whole blood, you can donate plasma up to two times every seven days, says Dr. Alan Mast, an expert with the American Society of Hematology and senior investigator at the BloodCenter of Wisconsin.

The first visit might take up to an hour and a half, Mast says. Be prepared to have a needle in your arm and undergo blood tests to make sure that you're not carrying certain diseases. "You need to be a healthy person," Mast says. If you're doing lots of drugs, having sex with prostitutes and engaging in other risky behaviors, you won't pass the screening.

In return for a relatively modest weekly donation of plasma, the payout can be substantial. If you donate once per week you can earn up to $400 a month, depending on your size, says Josh Patoka, founder of personal finance blog Money Buffalo, via email. He has investigated plasma donation as a money-making strategy and notes that the amount you're compensated will be tied to how much you can donate, which is linked to your weight. You'll typically receive payment on a prepaid debit card, he says.

When considering which plasma clinic to visit, Mast says, consider those that are IQPP-certified. A list of clinics with this certification can be found on DonatingPlasma.org .

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Donating Eggs

Women who are in their 20s – and maybe early 30s, depending on the clinic – may be able to earn between $6,000 and $8,000 or more for donating their eggs at a fertility clinic .

Donating your eggs is a more complex process than donating plasma: Be prepared for about two months of medical visits and procedures, which begin with screening, testing for diseases, counseling services and genetic tests. You'll be prescribed birth control pills for a certain time frame and self-inject medications for several weeks. After supercharging your egg production, a minor surgical procedure will remove the eggs, after which you'll be asked to lay off strenuous activity for a couple of weeks until you heal.

Despite the commitment, Mona doesn't see the process as too arduous. "It's easy money, and it's quick and a little painful at the end," she says.

For some donors, knowing that their biological material will be used to create new life – or lives – is incredibly gratifying. For others, it may be worrying to consider how current or potential future partners or offspring will feel if they learn you have biological children already existing in the world. Mona stresses that people need to research and consider these questions on their own. What works for one woman may not work for another.

Donating Sperm

Your gut reaction may be that donating sperm sounds much easier, more pleasurable and less time-consuming than donating eggs, but it's not so simple. "You can't be scared of needles if you're a sperm donor because you're going to be tested constantly," says Dr. Paul Turek, a board-certified reproductive urologist, male fertility specialist and director of The Turek Clinics in Beverly Hills, San Francisco and Silicon Valley.

The payout is good, but the commitment is more than you might expect. "At the end of the day, you probably make $500 to $2,000 per month at the most, with a weekly commitment at several times per week," Turek says.

Like egg donors, today's anonymous sperm donors must also undergo a list of federally required screenings, tests and be prepared to make a firm time commitment. "Sperm banking has gotten quite lucrative for donors," Turek says. "But you have to essentially be a perfect specimen to do it." You'll need to be tall enough, healthy enough and young enough to qualify. Turek estimates that about 1 percent of donors are accepted.

There are so many administrative, biological and genetic barriers that it's difficult to make it through the screening, Turek says. Then, you'll need to make a monthslong commitment – even up to a year – to provide a sample a couple of times per week. You'll likely need to visit the office during business hours, which is why it's a particularly attractive option for college students . Because there is an abstinence period required between donations, "it puts your love life to death," Turek says.

[Read: How to Negotiate Your Medical Bills .]

Again, you'll need to be comfortable with the fact that your biological material may create a human life and that, depending on how you structure your donation, your biological child – or children – may contact you when he or she turns 18.

Turek notes that there is an extra benefit to applying to donate sperm, even if you aren't ultimately selected. It gets young men, who are notoriously bad at routinely visiting the doctor, to actually get medical care, including screenings for STDs, reviewing medical and genetic conditions and more.

Other Medical Research and Donations

Outside of these options, there are myriad health care studies you can participate in for compensation at local teaching hospitals, universities and other health care facilities. Payments vary depending on the type of study you participate in and the commitment involved. People can also donate blood platelets, hair and other bodily materials. Consider your tolerance for pain, needles and sitting in doctor's offices, plus the long-term consequences of any donations you make, then determine whether this money-making path is right for you.

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