Nonamed

Hey guys, I'm rising junior at Purdue University, studying Electrical Engineering. FYI, I'm Asian (international), male. For my research experiences, I joined the lab in Purdue for 2 years and the other lab in Seoul National (Korea) for this summer. What I'm thinking of is to contact the lab in other US universities which I'm interested in to apply for the graduate program, and ask them if it's possible for me to join their lab without any payment during the summer (after my junior year) I feel like it's pretty common in Korea to contact the research lab prior to be enrolled and see rather the lab has same research fit, so I'm wondering if any of you done that before or have interested in. It looks like a win-win for both me and professor so that I know how the lab is like, and professor would have idea of me (if I'm ok as a researcher or whatever) I want to hear any comments from yall. ++ Does anyone know if the professor prefers the MS student or the MS + Ph.D student? I have low GPA without any publication so I'm just bit worried. Thanks in advance.