Some pet sitters charge a flat fee for 24-hour in-home care, but most of them adjust their fee if they are responsible for more than the "average" number of pets and livestock. Think about how long it takes you to care for your animals - it will take the sitters the same amount of time or LONGER since they are not as familiar with the routine. You have to be prepared to pay them for their time. They will be spending time at your house that could be spent doing 2 or 3 other sitting jobs and earning them more money than what you are paying them.
 
I don't have quite the same number of animals as you - I only have 3 horses, 3 goats, 1 steer, 4 dogs, 3 cats, 21 laying hens and 28 meat chicks. When I have to leave, I try to simplify everything for the sitters. Everything is color coded so the right species/animal gets the right feed (stall signs, labels, instructions, buckets are all the same color for each animal and/or species). I have detailed instructions posted in the barns where they are easily visible during feeding time (and they are printed on colored cardstock to match buckets, signs, etc.). My sitters really appreciate the organization, and reflect that in their price. They charge me LESS than my neighbors, even though I have 2x the number of animals.
 
I also let my in-home sitters have free access to my food and pantry, and even plan to get them gift cards to their favorite restaurant for their next stay. I want them to come back!