You do not get paid a lot in a PhD program. Where I am the pay is barely enough for one person to live on. There is also the time commitment -- a lot of programs demand 60 or more hours per week from their students. The combination basically means that starting a family is impossible while you are a PhD student, unless you have a spouse who has a comfortable income / family money.

If you do not mind a small adventure, consider moving to another country or continent. PhD positions in some countries (e.g. The Netherlands) are paid quite ok, with few distractions (usually fully focused on research), and a 40-hour work week.

Of course, there is good competition, so it might be harder to get such a position.

In Australia, with a scholarship and a few hours a week TAing during term time, I made enough to buy a half a million dollar apartment with my wife who was on a new-graduate nursing salary. She then got pregnant just as I finished up (good motivation to write fast, that was!)

YMMV but if you're thinking you're being used for cheap slave labour, you're in the wrong university.

I was a PhD student (I stopped to move to SF and work on startups- although now after 2 years I'm thinking of going back), and fwiw I enjoyed TA'ing. Grading papers was the worst part (but with a glass of beer and some motivating music it's not that bad), but I found everything else to be fairly rewarding.

You're right. I would just guess that most people are there there to learn and do research. And TA'ing takes away from that. But plenty of people do from PhD to teaching positions - in which case a TA'ship is perfect and gets your feet in the water.

I wouldn't necessarily agree that TA'ing takes away from teaching and learning. Many of the top researchers are also, in my experience, fantastic teachers.

I like to refer to Feynman's writings on this matter: http://www.pitt.edu/~druzdzel/feynman.html