Here's a tip contractors usually don't give you until it's too late: Get a lawyer.
My experience from three decades of building and remodeling homes in stringent Nantucket has taught me it's never too early to check regulations on what and where you can build. The penalty for ignorance—or for being obstinate—is paid in time and money.
Face the environmental facts. Because coastal areas are sensitive regions, you can expect restrictions about drainage and waste control, wetlands, foundations, and setbacks from the waterline. And where there are more rules, there are more opportunities to run afoul of them. Sure, real estate agents and sellers are obliged to warn about restrictions. But if they don't know or relay all limitations, your only recourse is to sue after the fact, when you're already deeply invested in the project. It could take years to recover losses.
Research community design rules. Longtime residents value not only their investment but also the look of their beloved neighborhood. They want officials to take local codes seriously?even the rules that sound a bit silly to outsiders. If you seek variances or fight local boards, you may be in for a long battle. Wouldn't it be better to know design limitations before you pick your lot or buy a house to remodel? And shouldn't those rules be a topic of discussion with your builder and architect before plans are drawn? I've seen powerful clients, used to getting their way in the business world, reduced to tears after years of appeals and rule fighting.
Pick professionals who've been there before. To avoid costly conflicts with local codes, use a design and construction team with experience building similar structures in the same location. They know the terrain, literally (site restrictions, septic tank concerns,etc.) and figuratively (regulatory hoops you'll have to jump through). Ask around. Find out the names of the plugged-in real estate lawyers. Check out local work of architects and builders, and talk to their customers.
Choose a community, not just a site. If you like the feel of a place?the predominant architectural styles, the way houses relate to one another, and how well they fit into the coastal environment?you are more likely to agree with restrictions that preserve that atmosphere. Even the silly ones.