D.D.
My child got it around 5 or 6. That's when we started. So my 4 year old is also on the plan now.
I pay for chores - but not all of them. Each of my kids have a list of standard "everyone has to help the house run" chores. They do not get paid for these chores. I also have a list of extra chores which they can do to earn $.
Standard chores include helping clear the dishes from the table after meals and emptying the dishwasher. Paid extras are things like helping me vaccuum on the weekend when we have a clean-up day or wiping counters in the kitchen.
My 8 year old has stuff he wants to buy, and so he's motivated by $. My 4 year old doesn't really have stuff he wants yet, so while he will help because he likes to help (which is great), he is not at all motivated by $ yet (I still pay him for doing extras to be fair, but he wouldn't notice if I didn't).