Im 18 and want to make money by being a tester?

I am currently a highschool student and need some extra cash to keep groceries in the house. I cannot get a job because i go to school from 6am to 3pm everyday, then have to take care of my mother for the rest of the night. She is bedridden and my sister goes to school at night. I have seen some stuff that you can try out new medicines and get paid for doing it. Im wondering where i can go or do to do this. As long as i can at least make 4 grand a month, im good. Any help?