As micheller has pointed out, if the person works in your home, you need to register as an employer and you will also need to pay at least minimum wage, deduct tax and USC (free payroll software available online) and do monthly/four-monthly returns for PAYE/PRSI/USC and have the added cost of employer PRSI. However, with three children, this could still work out at a better rate than a childminder or creche so it warrants looking into.