From time immemorial, salesmen have the reputation of being slick and dishonest. The trickery and deceptiveness of car salesmen have been brought out in such movies as Used Cars, and The Goods: Live Hard, Sell Hard. Many car dealers have gone a long way in proving these facts wrong. For a long time, car salesmen have been earning their bread through commissions. Finding a commission no matter the method used was crucial as this is what the salesman depended on to make a living.
Sleep applies to everyone. Everyone has to sleep though others do it longer or shorter than others. People usually sleep on mattresses.