It's pretty hard to be thrifty as a family in Tokyo, although it is possible in regional cities and in rural areas. It is generally accepted that the minimum a 2-child Japanese family can get by on, if mom is staying at home, is about JPY4.5M a year. This includes everything and assumes that the family is renting, but possibly saving a small amount each month for a mortgage on a house by the time the parents are in their late 30's or early 40's.