Wouldn't you say that a large part of a mortgage payment is actually an investment? If you were faced with large student loan payments, you could just decide to rent rather than take on a huge investment.
I'm wondering if you had a straight face on when you said "a large part of the mortgage payment is an investment". Either way: if they want to build a family, the rent vs. mortgage decision isn't going to change the equation much. Again, assume they have a kid. They have to factor in:
* Commute distance, which will determine how often they actually see their children.
* Lease security; it is extremely traumatic to move a school-age child to a new school district, or even just a new school.
* School quality: the places with the best rental stock are not necessarily places with acceptable public school, or accessible child care.
Again: the article's claim isn't that a couple can't survive on 200k. It's that they couldn't stay married. I can see reasons why.
Again, I don't see the problem.