Well my experience has been vastly different from everyone else so far. I married when I was 18, freshman year of college. My husband was 24. We lived, and still do, with my mother for financial reasons. We have been married about a year and a half now, but going strong 
We had a lot of stress early on, though. He has a considerable amount of personal debt and has struggled with depression and stress. I have struggled with stress. We are both now on medication for stress (I’m not joking). When we married, he was an illegal alien, with no family here in the US. I work part-time and go to school full-time, while he works full-time and goes to school part-time. Our house is very crowded. In a three bedroom house, we have my mother, my sister (who just turned 17), and my uncle (Starving Artist). To top this all off, we have three cats and three dogs, all of which are indoor pets. Space, who needs space? 
We do fight, and we have gone days without speaking to each other. It always works out in the end.
But we are happy together. I can’t imagine having married someone else, and I truly do want to spend the rest of my life with him. It will be interesting once we are finally on our own, though!