Are you talking about caring for someone else’s children in your home?
That would be a business service that you are providing for others. You would be expected to report the income on your tax return. You would probably be expected to come up with social security, medicare, etc in addition to income taxes.
If you care for children of more than one family you might be expected to apply for a daycare license.
Since this would be in your home, your clients would not be required to report the money paid to you but they might want to do so in order to optain a childcare credit or to obtain reimbursement from a pre-tax withholding account for childcare.