Don't forget to do the minimum that's expected at least. eg cleaning up after oneself. Putting dishes in the sink != cleaning up. Especially if they have time to do it.
It's amazing how much ROI you can get from things like that. I lived in utter peace, harmony, and sanitation with 2 roommates for a while, and the $90 we paid to have a maid come by every two weeks and clean the townhouse was money well spent.