Ah, a nice topic i haven't seen before. Was thinking myself of buying a small apartment with ocean views but prices are so prohibitive a ship of 14-15 meters or even some more would make more sense, even adding the price of the moorage. That way I would have as many ocean views as desired and a ship has always an extra cool factor. I have some notions about sailing and such as I have always been closely related to the sea and have used small zodiac boats for fishing and such. Never had a big boat though and should get the mandatory sailing license before buying one.
First thing to have in mind is sail versus motor. For the same length, a motorboat has always more living space, however fuel cost would be prohibitive and I don't like to navigate while hearing and smelling a diesel engine. Sail boat otoh are less habitable but you can sail almost for free (not counting changing sails every x years) and are extra cool. So if you want a boat to only live in it, an old motorboat or even a barge, if you want also to go out and navigate, a sail boat.
A main factor to have in mind is hull material. There are several options here:
-Fiber-glass is the most common and most balanced all things considered but with time water can affect it and develop some illness such as osmosis which are difficult and expensive to repair.
-Steel is the most resistant of all materials but salty water is extremely corrosive so you always will have a disc grinder in a hand and a paint bucket in the other one. It is relatively easy to repair though. It is also heavy and most adequate for large boats.
-A wood boat otoh if property built resists (salty) water the best, but requires some love, and rain water can rot it in a eyeblink. It is a good option for the sea, but you will learn carpentry like it or not.
-Aluminum is probably the best material for sail boats. It is light, resistant and won't rust, it is however hard to repair and expensive. Short circuits and such can be specially dangerous as a bad insulated wire can make a big hole in an aluminum hull in no time.
-Ferrocement boats otoh (yes there are boats made of cement) are sturdy, relatively cheap, easy to repair, fresh in summer and warm in winter and won't rust or rot or suffer of osmosis. Ferro cement is the most heavy of all though and just as steel not suitable for small ships under 16-17 meters. Weight makes them slower than other options too.
-There are also exotic materials as copper-nickel that are mostly perfect in every aspect and won't even get any fouling, but obviously are terribly expensive and boats made of this material are very rare.
So I would go with a ferrocement motorboat if the main goal is to live aboard and only get out of the harbor occasionally and a fiber-glass or aluminium sailboat if sailing is the main thing. A compromise solution would be a motorsailer, a bit of both worlds, can navigate with sails (kind of) and is more habitable than a pure sailboat of similar size.
About what equipment to install to make life aboard more self-sufficient such as solar panels, desalination plants and such it is a extensive topic, but space is always the most precious thing in a ship, and these things require space, so the bigger the ship the more possibilities in this sense. In my case I would always prefer to have a proper moorage with power, water and drain connections so it would not be an important aspect.
In any case a very complex and interesting topic and an option to consider given the price of houses, specially if you love the ocean.
