How much would you pay a manager in your small business?

Let’s say you have a small retail busines that brings you about $150k a year in your pocket before taxes. You hire a manager to relieve you of having to work so many hours. He is going to work full time, and his daily tasks will basically be what yours are when you’re working. He will work 40 hours and you will work about 50–60 still, splitting shifts with him, and also doing extras being the business owner. What do you think is a fair salary?