I work for a local health department. Here's the low-down. Entry level (no experience) MPH jobs make around 30-40k. You work for several years then try to get in to an administrative, management, or policy position. Those jobs pay the $100K you're looking for, but it could take forever to get one.
If you have some other qualification (ie: RN/MPH, MT/MPH, MD/MPH, research...), than that's not the case at all.
It also seems like applicants with an MPH do pretty well getting into med-school.
That Help?