Would you willingly suffer a bout of flu for $3,000? Scientists at the U.S. National Institutes of Health are hoping that at least 100 people are game. You’d get the satisfaction of helping advance our understanding of influenza, but also some cold cash.

The clinical-trial volunteer is a key link in the chain of medicine. Researchers might spend countless hours developing a flu vaccine, but volunteer research subjects are needed to make sure that treatments are both safe and effective. The value of contributing to research isn’t always enough to convince people to become human guinea pigs. A trio of researchers interviewed 80 trial volunteers for a study published in the journal BMC Public Health in 2013, asking them why they were signing up.

“The most frequently encountered motivations were financial gain and therapeutic alternative,” the authors wrote. “Altruism was not a common motivator, and when altruism was present, it was observed as a secondary motivator.”

Not all clinical trials pay, but researchers often find it necessary to sweeten the deal in order to induce people to give up their free time and, in some cases, try drugs that offer no health benefits or even some risks.

“Payment to research subjects for participation in studies is considered a … recruitment incentive,” the FDA says. “Financial incentives are most often used when health benefits to subjects are remote or nonexistent.”

So, it’s no accident that if you’re participation is riskier or more inconvenient, you’ll probably get paid more.

First, some tips to keep in mind, if you’re thinking of loaning your body to science:

- Compensation for clinical trials is taxable income! If you make more than $600, you’ll have to report it to the U.S. Internal Revenue Service, and the company or institution running the trial should give you a 1099 form.

- Read up before you sign up. Before you start in a clinical trial, you’ll be given what’s called an “informed consent” document that outlines the purpose of the trial, along with all the attendant risks and potential side effects, discomforts, benefits and more.

- Volunteering for trials may not be easy money. You might have to keep a diary of your symptoms throughout the process and make time for lots of doctor visits!

- Not all clinical trials will pay for transportation costs.

- Where can you find clinical trials seeking participants? The Center for Information and Study of Clinical Research Participation has a good search tool here; there’s also the NIH database and ClinicalTrials.gov. Nearby universities and research institutions will probably also have their own recruitment websites (for example, here’s  Columbia University’s.) There’s also a site called ResearchMatch where you fill out some information about yourself, and scientists will contact you if they think you’re a good fit for their study.

Just how much can you earn by becoming a lab rat? Well, it depends on a number of factors, but the primary ones are the type of trial you’re participating in and the kind of condition being studied.

A review by the Tufts Center for the Study of Drug Development (cited by CISCRP [PDF]) examined 6,000 clinical trials conducted between 2001 and 2007, and found that nearly two-thirds offered some level of monetary compensation. Phase I trials, where a drug is offered for the first time to healthy human subjects, are more likely to be paid and will pay out more -- an average of nearly $2,000 per volunteer across all disease areas, according to the Tufts analysis. Phase IV trials, which are conducted after a drug’s been approved, pay out the least -- an average of $400 per person, across all disease areas.

One of the big golden geese for would-be guinea pigs is sleep studies, which can often garner hundreds or thousands of dollars for a few weeks’ work. Heart disease, neurological, gastrointestinal, endocrine, and blood disorder studies also tend to pay in high amounts, according to CISCRP.

You can make even more money by just lying around if you manage to land a gig as one of NASA’s bed rest study subjects. The space agency is trying to see how astronauts’ health might be affected on long space flights by simulating those conditions on Earth. To do this, NASA scientists monitor how people’s bodies change after long periods of immobility.

And lest you be worried about entertainment, lying around for months doesn’t have to be completely boring. According to a 2008 Q&A with NASA research scientist Ronita Cromwell published in Wired, subjects have Internet access, computer games, TV monitors and even a common room where they can socialize with other subjects (while still lying prone). But ideally, you aren’t just looking to be a couch potato for three months.

“We require that subjects come in to the study with a goal -- something they can do that can pass the time and look forward to each day,” Cromwell told Wired. “It might be something like learning a language. I have someone who is continuing his employment. I have another subject who is looking to make a career change.”

However, there’s one aspect of the study that might be a deal breaker for some: no conjugal visits.

Earlier NASA bed-rest studies paid participants $5,000 a month for 90 days, but the agency is upping the ante slightly in its latest study. NASA’s currently accepting applicants for a 70-day tilted bed-rest experiment, where you’d spend almost every minute of every day lying prone on a bed that’s tilted slightly downward. One group of participants will be doing specific physical exercises to see if that mitigates the expected bone loss, muscle decay and cardiovascular impairment. If you can last the full study period (70 days of bed rest, plus some time at the facility before and after) there’s a cool $18,000 in it for you. Sound like your kind of thing? You can apply through this link right here.

And if you have a condition that can be treated by an experimental drug, but can’t participate in a clinical trial for whatever reason, you still might be able to get the treatment through “expanded access.” Drug manufacturers will sometimes make new drugs available to some patients outside of the clinical trial group.

So, potential guinea pigs, go forth and catch the flu, pop a pill, or lie around for science -- but know the risks, and know your worth!