They want the home page to be custom for each of the three areas so the domains might be:
Now I'm trying to figure the most "Google Friendly" way to structure it. Seems like I have a few options. I don't want to have to create three totally different looking websites. They would all use the same basic framework of a site but the content would be different (different wording and pictures).
(a) Have a main site zipcon.com where the navigation to each of the three departments links to each of the three other domains so the department content is not accessible via the zipcon.com base address so there is no duplicate pages. This would mean the main zipcon.com website would be pretty thin on content itself.
(b) Have all the content on the main zipcon.com domain, but host the other three domains and make the home pages for those domains go to the content of the department home pages of the zipcon.com site but prevent Googlebot from trying to index the three department domains so there isn't a duplicate content issue. Downside of this is that then the department domains are only good for putting on business cards or using for local business citations - although I doubt Google/Yelp/etc would let you get away with having all three listed separately unless you gave them separate addresses and phone numbers.
The goal is that we want to have separate collateral (business cards, brochures, and possible business listing citations) for each branch of the business and when someone searches for that particular niche of service, the home page for that service comes up before the main home page in the search results (which would only be possible using method a)
I suppose we could also eliminate using the zipcon.com base website all together. But if the three websites have the same underlying HTML/CSS/JS structure and just different wording and images, will Google still considering them "semi duplicate" sites and therefore negatively effect the rank?