Baby foods: First four months
The perfect food for infants up to age of 4 months is exclusively just breast milk.
Breast milk, Formula
The preferred baby food is breast milk. Breast milk contains protein structures, antibodies, and hormones that can not be duplicated in a baby formula.
Food and Drug Administration regulates the ingredients of baby formulas in United States and the products themselves are governed by the Infant Formula Safety Act. The baby formulas are fortified with iron. Newer formulas also contain DHA and ARA found in breast milk. The pediatrician will help you determine the best formula.
The cow's milk does not provide nutrients in right proportions, and is a poor source of iron. Also the proteins are not easily digestible by infants and may cause internal bleeding. Academy of Pediatricians recommends breast feeding till the age of one year, at which time infants should be switched over to whole cow's milk over six months. This recommendation assumes infant is taking egg yolk and meats. For vegetarian infants, the cow's milk should wait till the age of 18 months. How to wean infant off the breast milk?
It is rare that breast fed babies get constipated, formula fed babies do get constipated. Babies may be given apple juice or pear juice diluted with boiled cold water in equal parts to relieve constipation. One may have to switch to a low iron formula as a last choice.
There is no need for water, during first six months. If you do need water, do not use bottled or distilled water. Boil tap water, let it cool and use it.
Homemade Baby Formula
Technically, it is feasible to make baby formula at home using evaporated milk. You might even find some recipes on the Internet. I strongly suggest please, please don't make baby formula at home.