With an approximate combined income of 105k/year, this is how my expenses break down:
8750/month before taxes=5840/month after taxes.
We have a modest condo--620 square feet, with a monthly mortgage payment of 1250 (which is really good--we have a 3.625% 30 year loan).
1250- mortgage
230- HOA dues
250- gas
560- car loans
215- student loans
heat/elec- 150
cable- 100
food-600
tuition- 1575
pets- 150
car insurance- 125
phones-paid for by our parents
Parking spot rental- 60
storage unit rental- 50
misc. expenses (oil changes, car registration, admissions, prescriptions, presents for family birthdays, etc.)-- 250
that leaves about 275/month for savings. Definitely not enough to start a family.
We're buying a house so that mortgage is about to increase from 1250 to 2500. We'll be able to handle this because the tuition expenses will end. However, it will take paying off the loans and getting some raises to afford having babies. We could have bought a less expensive house, but it wouldn't have been as good of an investment--we bought a fixer with a great location over a nicer house with a crappy one.
So is it possible to live off of and start a family with two 30k/year jobs...probably, but for some, the goal isn't just "making it work" it's living comfortably in a neighborhood you want to live in, a house that you like, and having cars/cell phones/cable and decent food.