MD and PhD programs are hard. No doubt. That being said, with tenacity, it is doable. In my post graduate program, we were paid a low stipend. It was so low that I shared a one bedroom apartment with two others. Yes, we slept in bunk beds in our 20s. We developed a morning routine. One would shower while another would eat, then swap. Then we would wake up the third roommate. We would share things, as roommates do. Waffles for breakfast? First one up made the batter and their waffle. Then as we made our way out of the house in the morning, each of us cooked our own. I had a bike but no car. I didnt eat out a lot, etc.
But we had so many friends. We were all in the same boat. None of us were rich, but it was one of the richest times of my life. I was single, yes, but a majority of my friends did have kids (some of them more than one and a spouse without a work permit to support). Friends go a long way. It was an extended family that we got to pick for ourselves. I did my share of babysitting for friend's kids while they studied for tests, did night shifts, etc. and loved every minute of the distraction.
We didn't have expensive things, but I never felt poor during that time (and I was). I was stressed, for sure, but also focussed on the end product.
Sure, there were rough times. It is not easy. Life isnt easy though with or without he MD or PhD. program (or even the title).
Hindsight is 20/20. I can say this now. If I could go back to any period of time in my life and do it over again, it would probably be this time of my life. I wouldn't go back just because of the degree that I have now, but because the experience, in retrospect, was THAT good.
I will say that if you are the type of person to believe the friends that say it cannot be done, it probably can't. It takes more tenacity than that. If you are a "finisher" that is determined enough to get it done, and has the grades and can get accepted....go for it.
The worst thing is having regrets.