How to Work with a Baby in tow

I have the experience of working with a baby in tow. A 7.5mo baby who does not know how to crawl yet but can sit already, a very clingy baby and a fully breastfeed baby too! I definitely can't work without a helper so I brought my eldest 9yo daughter with me to help me carry his baby brother when there is customer to attend too. Simple task like unlocking the computers for the customer to use, receiving money and returning the change, I will let her do. She learns how to count money, mentally which she is still not so good at it. But it is tiring for me because I cannot lie down from the moment I wake up till my bedtime. On that day, I slept before 12mn and woke up after 9am! I have not been sleeping more that 6 hours since I have my baby. That is how tiring it is to work with a baby in tow. It was not just the work at the shop. I still have to complete my housechores before going to work. Upon coming back home, I have to continue what I left behind and attend to my other children too. Still, we are still not earning enough for the family. :(