The six properties -- all of which are abandoned and essentially obsolete -- include five towers on Lake Michigan and one on Chesapeake Bay. The US General Services Administration is the government office overseeing the auction, and it's accepting starting bids from $10,000 to $15,000 for the structures, which is an absolute steal when you consider what it might cost to score a proper waterfront home in a similar location.
However, there are a few caveats. For one, even if you successfully win the auction, the property each lighthouse sits on will remain owned by the government. Additionally, prospective bidders must be prepared to repair and renovate each structure so that it's up to code for civilian visitors, which could end up being pretty costly since several of them are in pretty rough shape. Then again, once you whip it into shape, you'd likely make your money back pretty quickly if you list it on Airbnb for a bit.
Here's some more info on each lighthouse, including their current high bids as of Monday afternoon: