I have a business and..?

I am making a cover letter to send out to businesses such as real estate agencies, for our painting company, and I was wondering when I write the first line what should it say? To whom it may concern, Dear *whatever the name of the business is* etc, if you have other ideas as well that would be great, I'm just brainstorming right now and trying to figure out what it should say to sound the most professional. Thanks!