here's another Chesapeake Bay lighthouse you can buy-- for a mere $249,500. (The price includes a property onshore from which you could launch a boat to get to the lighthouse.) It's named the Wolf Trap Light Station, it dates from 1894, and it's three miles offshore. It (like Thimble Shoal Light) is a "caisson" style lighthouse, its light still functions (and is operated by computer), and its living area (which hasn't been occupied for some time and would require renovation) is about 1500 square feet.
The picture is from Wikipedia and appears to show the lighthouse in happier, shinier days. You'll notice it looks substantially more run down in the picture accompanying the article.
For me, there are some days when living three miles offshore really does sound like paradise!