Side effects: Before any trial starts you'll be presented with a list of expected/possible side effects (and possibility probabilities depending on the stage of the trial. This will before you sign the consent form and should be discussed with you fully.

The side effects will depend entirely upon the compound/procedure/sample being tested. Biopsy studies will leave you with a sore muscle (comparable to having a deep muscle vaccination) and a slight skin lesion. Scans, depending on the type of scan you can be entirely side-effect free to having some nausea. Medications: entirely dependent on how you react the the particular drug being studied. I've have some bad pretty awful side effects including but not limited to: stomach cramps, nausea and vomiting, constipation, diarrhea, dizziness, numbness, tingling, bradycardia tachycardia, blood pressure fluctuations, flu-like symptoms, muscle pain, breathing issues (related to asthma studies), partial blindness, toothache, vertigo, hair loss, excessive tiredness...

Time: On a day-to-day basis, the impact is minimal. However, trials usually begin with an overnight(s) stay at a clinic and require regular appointments (and/or stays) before the end, which itself usually requires a comprehensive assessment and observations overnight. It varies trial to trial. I've had trials with only 2 in-person appointments across several weeks but then others will require many periods of staying overnight. The longest being 21 days. The longer stays did have an impact on my studies because I needed to rely on other people recording my lectures/seminars and couldn't attend tutorials or labs. On the plus side, staying in a clinic is pretty dull so there's plenty of studying time and traveling to clinics usually leads to a lot of train time.

Screening process: This should be made clear in the initial advertisement and appointment. There will be a list of qualifying and disqualifying criteria. If you meet what is stated on paper, you'll usually be invited for a physical and further discussion. Depending on the trial, you may then be entered into an initial stage to see if you meet all requirements and will have to keep a diary or carry out certain activities. If you're started on the trial they'll usually be a review after a couple of weeks to see how you're responding. At this point, you could be removed from the trial depending on what they're looking at and how you respond to whatever it is being studied. Just don't lie about anything.

Money: It isn't a fast pay off. You've got to be in it for the long game to make it worth while. If you get removed from a study at the mid-way point or before the remuneration is pretty terrible. Money usually increases with the level of risk, effort and invasion. I don't want to talk specific figures because you need to decide for yourself what is and is not acceptable. My highest paying was a 6month study and I made 5k having biopsies 3-4 times a month whilst taking a cocktail of proteins and doing high intensity interval training every day. The lowest was $100 for providing some tissue samples.