SEOUL — The cellphone bill was coming due. The pricey medication for her chronic skin condition was running low. She’d already tapped the parental credit line, promising to pay them back in monthly installments. In her bank account, less than 50,000 won — not quite $45. A few months into the COVID-19 pandemic, most of the typical part-time gigs 23-year-old Lee Ho-jung usually relied on had vanished. Restaurants, bars and supermarkets were laying off workers. Dozens, if not hundreds of applicants were flocking to minimum-wage jobs with limited hours. So Lee turned to what has increasingly become a last recourse for young South Koreans in need of quick cash: enrolling in clinical trials.