Um, babies cost more than $500 a month... just sayin'. I pay $125 a WEEK in childcare alone. Diapers are $20 a box and a box lasts maybe 1/2 a week for a newborn. Formula is $11 a can and lasts about 2 days. Then there's baby food, cups, wipes, etc, etc, etc... it adds up to closer to $500 a WEEK, than $500 a month. Then there's clothes, baby gear - like strollers, cribs, carriers, car seats, LIFE INSURANCE, etc.
I'm not saying you should wait until you're "financially ready" b/c that'll never happen, but if you want one of you to stay home, you will need to wait a while for sure.