My main business is in direct marketing (I.e. D2D, B2B etc.)
I don't think it would be a very lucrative idea. A lot of driving around and you are still probably not going to get to the decision maker. Better off calling.
I once had an idea to find small businesses that didn't have a domain/website and just register and create a site for them, and then attempt to sell the package to them with a yearly hosting fee. More time and energy than I can spare, but it has potential.
Good luck