About seven. When they're little 2 and 3 (heck even my 1 year old) I help them clean. They pick up toys and put them where I tell them too. I do the vacuuming and put their clothes away (though they do try to help). By about four I stop doing as much and basically give them a couple tasks at a time "Pick up all your blocks and put them in your block bags," "Put your dress up clothes in the closet," "Put your teddy bear on your bed," and for the most part they do all the pick up and I just give direction while being nearby if they start having a melt down. By five I give two or three tasks "pick up the toys, throw away the trash, and put your dirty clothes in the hamper" then walk away and just check on them every now and then. By seven I should be able to say "Clean your room, give them some time, check in and point out what they're missing and leave them be for a while longer. My SD is almost 10 now and has been cleaning her room on her own since she was seven. She'll come tell me "I'm done," I'll go and point out the one corner she always misses, she picks that area up and then if the floor needs to be vacuumed she'll do that too.