Sadly $300k is not unusual at all. My folks couldn't help out either. But fortunately it's very manageable. If you end up in ortho spine, neurosurg, etc., $300k is a non-issue. It'll balloon even during residency, but specialties that pay that high can easily payoff that debt in 2-3 years if they don't buy a boat right away (and maybe even if they do). If you go into a lower paying specialty like me, it's still doable, but you have to go into attendinghood with lower expectations unless you want to be in debt your whole life.
First step: Read and subscribe to whitecoatinvestor.com articles/blogs. He has a "new to the blog" or "start here" or something like that for newcomers. Start thinking now about how to minimize/payoff your debt. If you can borrow $5k less each year, and still be comfortable enough, then that saves you $20k plus another $5-10k in interest. If I had known about WCI's website earlier, I think I could've borrowed less and started repaying a more significant amount as a resident. When you're in a lower-paying specialty like me (PM&R), it makes a more significant impact on your post-residency lifestyle.
"Comfortable enough" is a relative term. I knew some classmates with huge 2bd apartments downtown. If you're single, you should really be getting a studio or sharing a place with a roommate. Get a cheap, but not unsafe, place to live. If you don't have a car yet, live within biking distance of campus--the odds are you won't need a car regularly until M3. You'll probably need one occasionally up until then, but classmates/Uber can get you by. If you're not making those car/gas/insurance/parking payments, it can save you a lot. You will need a car anyway, so the reality is it just pushes your car purchase back two years, but if you buy a 2010 now vs a 2012 in M3, that's a newer/more reliable car you go into residency with. (Don't buy a clunker--you need something reliable in residency. Be thrifty-not cheap).
If you really want to be hardcore, check out mrmoneymoustache.com. That guy really knows how to be thrifty and save money. WCI argues he's a little more extreme on the lowering costs and not maximizing earnings as much as he could, but as a med student you have no earnings you can maximize, and you shouldn't choose your specialty on expected salary. The more comfortable you feel with your debt, the less pressured you'll feel to choose a specialty based on it.
