Depends on where they live[1], there are several states that didn't expand Medicaid under the ACA. They'd also have to make under 100-138% of the federal poverty level, which is ~$12,490-17,236.20 for individuals and ~$16,910-23,335.80 for couples.

[1] https://www.kff.org/medicaid/issue-brief/status-of-state-med...