Nexus for Michigan when you have a business out of state?

Anyone know about Nexus in Michigan? I have a friend who comes to the state for help in my work during my busy season. I pay him and give him a 1099 at year end. He also mentioned some of his friends for my company. They live in Michigan, the goods are sent directly from my supplier. Perhaps the $ 2000 sales in the last 7 years. I am responsible for Nexus?