A freind of mine is building a steel hulled live aboard boat about 40' in lenght along more or less trawler lines. The goal is a very seaworthy boat for Alaskan waters. It has so far been a multiyear project that will still consume 6 figures before it is finished.
I strongly disagree regarding a steel hull and aluminum superstructure. The dissimilar metals will cause no end of problems over the life of the boat.
A better approach is a composite superstructure of wood encapsulated in fiberglass and epoxy resin. With that approach you get great strenght and comparatively low weight. Dry rot is not an issue if it is properly built with careful attention to detail, such as sealing all holes in the wood with epoxy (as in all screw holes, etc.) When properly built, you could roll the boat over or run it completely under green water over the bow and not lose the superstructure.
I'd also argue that wood is not a bad choice for a larger live aboard type vessel from a strenght perspective as wood tends to remain flexible and will survive conditions that may crack or separate the plates on a steel hull. There are after all still wooden WWII era mine sweepers still in use in excellent condition. The downside of a wooden boat is the labor involved in construction and the need to either fully encapsulate the wood in fiberglass and resin or endure no end of on-going maintenance and the penalty for slacking off on maintenance can be very rapid deterioration. On the other hand, steel hulls also last for decades, but over time oxidation can thin the hull plates to half their original thickness making them uneconomical to refit. High quality sacrificial anodes replaced frequently are important on a steel hull.
Selling a one off boat creates some unique issues as the engineering and equipment is going to be scrutinized to a much greater degree. But that can be minimized if you build your own boat by building to a well known and known to be very seaworthy design.
I have considered building my own sailboat boat in the 36-40' range from time to time and have considered both steel and wood. Either steel or wood properly designed and constructed will last decades. Steel is potentially faster to frame, but requires more equipment as the pieces are larger, the steel needs sandblasting before priming and painting, and the hull lines suffer if you are limited to flat plate steel in construction. Wood boats go together with smaller and lighter peices and can more be easily built to much cleaner lines but require more fabrication and extensive use of fiberglass and resin. So there are pros and cons each way.
In either case the arguments for building your own boat come down to reducing your investment through sweat equity while simultaneously peading the outlay of cash over a period of years while you build the boat. Construction of wood boats in particular appeal to those who enjoy building wood boats and/or who enjoy the beauty of a wood boat.
Buying a used boat in need of a serious refit at a comensurately low price is a great option as an extensive rebuild is still much cheaper and easier than building your own. That said, dry rot in a balsa cored fiberglass boat can get extremely expensive and time consuming to repair. So if you go that route CAREFULLY inspect the fiberglass and core, particularly around any holes that have ever been put into the glass. Any softness will mean potentially expansive removal and replacement of the core material. Foam core fiberglass boats are more forgiving in that regard, but are also not as strong for a given thickness of material. Spider cracks in the glass can also be very time consuming to repair.
