iomhaigh's estimates for what living costs were extremely conservative. That said, you will be able to get by fine on a combined $35K, since you will be living in a cheap town. My point is that just because you have been able to get by on very little money thus far doesn't mean that you will be able to keep it up during grad school.
Oseph is dead on here (and throughout). Lest I lead anyone astray, I was in a cheap part of the country. I'd double that whole thing for an expensive area.
Oh, only too true. My stipend puts me at making about half of what someone living right at the poverty level in my area makes. Spouse and I have been lucky because of generous family, but even then we are leaving with not insignificant debt.
It's such a weird thing, figuring out strategies here. I was offered a moderate funding package at a good program in an expensive area and a generous funding package at a respectable program in a very inexpensive area. I took the moderate funding at the good program in part because I figured it would help my job chances. I was right -- I got offered a good job. On the other hand, it took me much longer to finish, because of teaching to pay the bills (although I think all the teaching helped me on the market too), I was under much more stress because of financial worry, which damaged my health, and this strategy can really backfire if you end up finishing with substantial debt. I have had friends here at moderate funding school/expensive area finish, not do so well on the market right out (just because they are ABD -- the program is still good), and then they aren't in a position to wait it out with some adjunct teaching until the next go-round, because they have huge bills to pay -- so they go into 'real world' jobs and never get out again. On the other hand, I've seen people at the not-as-good program strike out first time on the market, but, because they have little to no debt and in some cases a small savings cushion, they are able to ride it out another year with just a little adjunct teaching and then get jobs the second time around. So it is a gamble. Good luck! Honestly I'd go where you like the people/ideas best, and then just keep being thrifty (within reason).