I am currently starting a mentoring / consulting business with a program for acquiring a customer base for startup and developing construction companies out of the Chicago area.  

For construction you start with the plan rooms and bid sites, unless your target market is residential. Web based marketing my give you a couple of projects a year, depending on how much you put into it, but the majority of project would be won from bidding off bid sites with a strong focus on repeat business.

You start with cherry pick your favorite projects to bid on. Then you need to know how to get your foot in the door.