You can summon a hell horse for any task. The bigger the task or the worse the task, the more of your life force it costs you. If it costs you all your life force they get your soul. Thankfully summoning one costs you less of your life force to clean your house than it would take to just do it yourself. They get grumpy when you haul them all the way up from the deepest pits of Tartarus just to do your chores for you though, so the classy thing is to treat them with dark chocolate or devil's food cake when they're done :P