I'm currently working on two seperate projects. A remodeling job (exterior and interior) and getting paid as the client gets the cash from the bank. Almost everything we are doing on this cabin is done in a step-by-step process with the owner.
On another job we are doing a very large residential landscaping project (approx. 25k into it and is looking at another 35k). The client on this project has always wanted to be a landscaper and is very excited about the prospect of ordering materials, doing planting, etc. We are primarly doing the dirt and walls.
On the cabin job, we go with the client to do the ordering of materials, charge for labor via particular job, etc. The nice thing is the client sees where the money goes and simply can't complain. We charge for all our time educating the customer on materials and picking them out with the customer. Sometimes she micromanages a bit to much, but over a 3 month period things are smooth now and our boundries are very set.
On the landscaping project, its can be a nightmare at times. Shes orders materials not needed, over orders, and has them placed in all the wrong spots.
The Moral: I will never allow a customer to order materials and manage the deliveries. If it was a project that was to good to pass up, I would tell them I have to be there for all the ordering of materials and need to be apart of all deliveries (if they want to be in charge of that aspect) and will be paid for that time. If you layout the plan for your situation with timelines, budgets, and the above moral - you could pull this off with a lot less headaches. But be upfront now, or expect to be misrable.