If you and your partner both work full time, factor 20k+/kid/year for child care. If you later send your children to private schools, factor roughly the same rate.

If instead you choose to send your kids to a public school that provides good educational opportunities, factor in either several thousand in additional local property taxes [1] or similar amounts in donations to the school PTA [2].

[1] http://www.paloaltopulse.com/2014/10/16/palo-alto-pulse-asks...

[2] http://capta.org/pta-leaders/run-your-pta/finance/fundraisin...