Why Child Support May Be Necessary
Child support depends on both the costs of providing for your children, and the income that you and your spouse have available with which to meet their needs. If you and your spouse share physical custody, you'll each maintain a residence for your children, and you'll each pay for their needs directly on a roughly equal basis. Therefore, if you earn about the same, neither of you should owe child support to the other. If one of you earns significantly more, however, the parent with the greater income may have to pay child support to the other so that your children enjoy the same standard of living in both homes.
The Effect of Legal Custody
There are two types of custody – legal and physical. Physical custody relates to where the kids live, and legal custody involves which parent makes primary decisions regarding child-rearing and care. Joint legal custody is common, and it has no effect on child support because making decisions for your children doesn't incur costs.