You would also want to know if there is a risk to you by participating in the research and if there would be any charges to you or your insurance company. Most research is funded totally by either a grant or the institution conducting the research. All research plans must be reviewed by that institution's review board for the use of human subjects, so that they can evaluate the ethical use and the amount of risk to the prospective participant. These results should be available to you if you inquire. You will also want to know how many visits the research will require and evaluate your personal situation to see if this is a possibility for you.
Some research programs require only yearly evaluations.
Others may require weekly or even more frequent visits. This follow-up is extremely important to the physician or institution, so try to be fair in evaluating this aspect. I do not mean to imply that this is not important, because answers often come from the knowledge gained by understanding the cause. Muscle biopsies or spinal fluid studies are invasive and increase the risk to the subject. If you participate in such a study, you might want to be informed not only of the risks, but also who will finance the treatment and costs if complications occur.