Just give them a lot of plain metal furniture and a tiled floor, and if they don't tidy it when you tell 'em to, take a firehose to it.
Pssh, and they say parenting is hard.
When he was younger we cleaned it together. As he got older I just closed the door. This way he learned how nice it is to have a clean room and that if it's going to be clean, he'll have to do it himself. It worked, because today he is 25 and he keeps a nice house even though his bedroom was a complete disaster through his teen years.
My kids are very good, they learned from me over the years, just hide everything in the closet
I made them clean their own....
Convince them to do it themselves?