Adding New Listings For Non Administrators

on http://www.rehabfinder.info, I want to make it, so that any one who owns a rehab can add a free rehab listing. However, I tried creating an account, and although it does make them account they are unable to add a list under the [custom_fields_block] that we had assigned for them. Is there anyone who can help us out here, so that the public of individuals who own rehabilitation centers can add listings just list an admin could but have access to no other part of the site and only add one listing instead of creating like 100 to spam the site? Any help would be greatly appreciative.