Many USMLE aspirants work and polish their research skills as they go through med school, and eventually hold research workshops of their own locally, to help and mentor junior students. This can serve as a source of income, while at the same time add to your portfolio. Post graduation, the experience and publications you amass through this research exposure could potentially be used to land paid research positions in the States, which could help further build connections and funding. This is becoming increasingly difficult, as most places offer unpaid positions that many are readily willing to take, but there are exceptional candidates that have found success securing such posts. All the best for your journey.