Once they're over 5, pay them seriously slave labour rates to do basic household chores. (Eg 5p for dusting living room.. properly.. 20p for whole house. 10p to hoover bedroom, 20p for whole upstairs.) They thinks it's big money, especially if it's all in small coins that rattle a lot. This works for a good few years before they learn the true value of money, and small children can be very good work horses.
By the time they are 7 they can be taught to safely make you tea and toast.
They can fetch you things you lay on the sofa, from 18 months. Praise them lots. You'll have a willing and unpaid servant for a good few years. Before you need to start with slave labour wages.