When I first started charging for my work, I learned an early lesson - nothing is as fast or easy as you expect. Calculate your material cost and add 15-20% since lumber never comes in the size you need. Make sure that your labor price is more than your materials - sounds funny, but early on I used to think that if the materials were expensive, I needed to back off on labor cost to keep the price palatable. Bad idea on my part.
Based on the projects I have done the past several years, labor is usually about two times what the material cost is in my small shop. Good luck, I hope you make some money on the project and have fun doing it!
Be careful, the woodworking "hobby" I have always loved feels more like work every night when I get home and head into the shop. Getting paid for work can turn your hobby into something less fun.