This is an unmet need. You could either build a site which list many contractors (several of these exist) or set businesses up with a small brochure site so that people searching on the web can see why they ought to call that particular contractor.
I agree with Fusion. I have had many contractors as clients and it isn`t as much that they don`t know about websites;they use direct mail coupons, listing in the trade blue book, listing in newspapers under services--more local advertising.
However, if it is another region then the Los Angeles area,the scenario will be different.
Most cities have a local contractors association. You could contact the association with an idea to list all the contractors under one web site. Each contractor would pay to be listed. Such a site exists that serve the