Many combined programs (MD/DO-MPH) do not have additional tuition and fees for the MPH, though some do. There may be funding available - check with your particular school. Some residency programs have funding set aside to help residents pursue graduate degrees including MPH. Many preventive medicine residencies will pay tuition and fees to fund an MPH, but you should check with each individual program. Primary care residencies may also have funds set aside for working towards an MPH. There are fellowships in many different fields which may also totally or partially fund an MPH, e.g. family planning fellowship for obstetrics and gynecology. Again, check with individual programs. And when it doubt, google "MPH scholarship".