Greetings Robert,
If you are looking to plant regular "woods run" black walnut seedlings, you can probably expect the following costs here in Illinois:
Planting Density: 436 trees/acre (10' x 10' spacing) Seedling $/acre: $0.50/tree or $218/acre
Site Preparation: $10-40/acre (ex: tillage & herbicide)
Tree Planting Labor/acre: $0.25/tree or $110/acre
Plantation Herbicide Application: $30-40/acre
Please note that there are numerous state and federal reforestation programs available to eligible landowners in Illinois. These programs may be viewed on my website: http://web.extension.uiuc.edu/forestry/tree_planting.html
To determine your eligibility for cost-share assistance or financial incentives, please contact your local Illinois Dept. of Natural Resources forester or your local USDA Service Center (Farm Service Agency).
Purdue University and USDA Forest Service has some wonderful publications to get you started:
http://www.ces.purdue.edu/extmedia/FNR/FNR-119.html
http://www.ces.purdue.edu/extmedia/FNR/FNR-149.html
http://www.ncrs.fs.fed.us/pubs/wn/walnutnotestoc.html
http://web.extension.uiuc.edu/forestry/publications/pdf/black_walnut/USFS_6th_WCRC_GTR_NC243.pdf
Best of luck!