You better have a lot of money, or the bank you borrow from better have a lot of money if you want to build a big boat. Have you talked with any builders/finishers? They will get you in the ballpark if you tell them what you want. In probably 5 minutes you could give them a quick run down on what you are looking for. The guys at Calvin Beal, H&H, and Wesmac are all super nice guys. All three of those companies took a lot of time with me on the phone and at their shops, and I was only looking for a bare hull. They treated me like I had a million dollars to spend, when I was only looking for a $35k hull.
Most the guys on here, including me, are just shooting blind in the dark on what a new 47'-50' downeast is going to cost. Here is a new
42x15 Calvin Beal that is very basic for $367,000. It's so basic, it would need a number of things added to it before it could go working, so add in another $30k - $50k. Obviously a 47 H&H is going to be a lot more than this smaller 42 CB. And the 50 Wesmac, hold onto your hat, it's going to be more than the 47 H&H. My guess to turnkey a basic 47 H&H with the systems you need, probably $475,000+. A basic 50' Wesmac, who knows, $625,000+? When I say basic, I mean you might get a toilet, a chartplotter, a chair to sit on, and a few windows to keep the weather out of the cabin. We're not talking big deck lights, gensets, elaborate electronics, hot water heaters, bow thrusters, accent stripes, stereos, comfy bunk cushions; those all cost extra

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