If you were going to take photos of Ford cars with the Ford logo for the Ford company for their ads and marketing, that would be commercial use; you would contract for the photos, the amount and type of usage, time frame, etc.
If you took a photo of a Ford for your own personal use or to use as a fine art print (for the personal use of the buyer) you shouldn't need permission. If you took the photo at say, a car show (that was publicly in view) for your local newspaper you would contract that as editorial use.
If you took a picture of a Ford with its trademarked logo and wanted to put it on T shirts or mugs, that would be retail use; if you took the photo to try to use for marketing your business or any other business purposes that would be commercial use - for both of those you'd need permission from the Ford company.
With this situation, I think it's more than we can figure out on a message board and you'll need to get information from pro photographers organizations, or even try your local art community nonprofits for info. If the artist isn't connected to any local art resources in the community and/or doesn't understand licensing etc. I don't know what else you can do but explain it the best you can. Maybe you'll need to provide the photos you took for the artist to use online for his intended purpose and leave it at that.