If you have to pay $30,000/year x 4 years, your choice is to pay with time in service at a location of the government's selection, possibly in a speciality or on a timetable of the government's selection to meet 'the needs of the Service.'
The alternative is to avoid the annoyance and the painful uncerainty of being treated like a cipher, and to repay in dollars alone, instead of in frustration and disappointment. Details follow.
1. If they need you to do a military internship, you will serve a military internship.
2. If they need more of a particular specialty, you may be directed that way.
3. Ask about going straight through internship and residency before payback.
4. If you do not go straight through residency, will you have to repeat internship?
5. How will the Medicare funding of graduate education affect your ability to return to a residency, or to change residencies in case you change your career choice?
6. What are the exact numbers (applicants to residencies in your chosen specialty)/(number of positions available) over the last 20 years? Don't settle for percentages. You want the numbers.