After I told you they would just go to big orange depot and buy the wood. Before I retired I was making $34 an hour as a UPS driver, I certainly wouldn't do it for less. I mow a few lawns now for exercise and some spending change. My 52 inch walk behind costs $6500 new. My minimum charge for mowing is $50 an hour. To be honest, I think it would be quicker to mill 6X8 beams and build a log cabin style barn. To answer your question, find an hourly rate you are happy with, and present that to them. No matter, your price will be way more than they could buy the lumber for, Joe.