There is very little financial aid for medical school. Students can graduate from med school often $300,000 in debt if they also did undergrad on loans.
Medicine is still a relatively lucrative career but the pay-off is NOT what it used to be and certainly is not as much as it now is for lawyers (who get through training in 3 years + clerkship).
Some training tracks are shorter than others, the shortest being to Primary Care, which is also the lowest paid gig. 4 years of med school + 3 years residency. If you subspecialize, you are looking at least at 3 years more of fellowship, if not four. You'll get paid a modest salary for residency and fellowship and so won't slip deeper into debt (much) for that training but you won't see any serious money until you are in your 30s.
For males, this deferred pay-off is often acceptable, particularly if they feel the calling to be a doctor and meet a nice woman along the way to start a family. For women, this is often a brutal compromise, as the nature of the training makes it very difficult to have children until it is almost too late. There are a lucky few who find good men to help shoulder the burden of family life and these few have kids in med school and residency.
The bottom line is that the bulk of the training requires and average of 80 hours a week of work (sometimes much more) for between 7 and 11 years of the rest of your youth. The rewards can be many but the reality of medical training is that it is not for the faint-hearted. You've got to believe in what you are doing; anyone who starts with the plan that they can also train to be an olympic level runner (simultaneously) will either have to be the most talented runner or is delusional. Even Eric Heiden postponed med school until after he was done with professional sports.