MPH's could be helpful, depending on which road you end up pursuing. Will they cost extra? Yes. Financing these in addition to med school may already make it not worth it to you. You probably don't need to worry about the additional workload though, because usually you would just take an extra year. One other consideration is that you could apply during your second year, or later like after residency when you have more solidified career goals and could apply to a more prestigious program. (i.e. Harvard or John Hopkins rather than whatever school you get into, unless of course that is where you are going, in which case congratulations).