syracusa- I would say the budget will be depended on the adventurous mind of the cook/shopper. Is your sister going to be the cook/shopper now that she will stay home with the baby? Who is the cook in the family? First, you need a stockpile in the pantry and freezer. Once you have a minimum of a 3 month supply of "stuff" on hand then you can buy the "specials". If I find a killer price on lets say coffee or chicken legs or canned vegetables- I can buy $100 worth because I really do not need anything else except fresh vegetables (Aldi's) and milk. Buy only the sale items each week and use what you have on the shelf. Rice is 3 lbs for $1 at Deals or Dollar Tree- do you know how many meals that is? OK- top of my head - you should spend no more than $300/ month for 3 adults and one baby.
lynclarke