Most consulting foresters in the Midwest charge an 8-10% commission for all work associated w/ the timber sale (tree marking, boundary marking, timber sale announcement, marketing the sale to multiple buyers, sale contract administration, monitoring the logging operation, etc.).
Some professional consulting foresters may even include a timber basis valuation for your accountant come IRS tax season; however, most consultants will charge extra for your timber tax basis due to the simple fact that it will require an extra day out in the field to collect supplemental forest inventory data.
I'm unfamiliar with professional forester timber sale compensation practices in Louisiana: by commission, by job, by hour, by acre, by volume, etc.
The easiest way for you to find the answer to that question is to simply contact an LSU Extension Forester or a Louisiana state forester:
LSU Extension Forestry: http://www.lsuagcenter.com/en/environment/forestry/
Best of luck!