If you have an expensive medical condition, you might consider the free health care of a study that includes travel pay. See ClinicalTrials.gov for those.

Or, if you're healthy, you can be a healthy human subject for medical research studies, like me. I'm spending the month of October at a medical clinic so they can test a minute amount of a new drug on me intended to help hypoparathyroidism. In exchange, I'll collect, $15,075. I've already received half of that. If you're interested, it's worth traveling to other states to do them. Many are paying over $10k currently. You can see them on the website StudyScavenger.com or JALR.Org, which stands for Just Another Lab Rat.

Canada has some also:
Toronto: [BioPharmaServices.com] (https://www.BioPharmaServices.com), PharmaMedica.com,
ToNovum.com, AtCliantha.com
Montreal: ParticipantsMtl.AltaSciences.com