I learned a few years ago about barnacles, which by virtue of being unaerodynamic and super heavy if you let them form huge colonies on the bottom of your ship, can decrease fuel efficiency severely. I saw how much work maintanence was, I said 'nope!' I guess a house is similar in some ways. Shingles don't last forever, pipes get corroded. The salty sea though, it's a bit more unkind to things, aye?
If you use anti-fouling bottom paint and either a) live in a region where it's pleasant to dive and scrub your hull, or b) can pay a service to do it for you, either way it's only a once a month thing, and a haul out ever couple of years. Although I can't speak to steel hulls, with fiberglass water can get into the fiberglass causing blisters that have to be ground out and epoxied in, which is precisely as annoying and expensive as it sounds.
Compared to a house an ocean going (so salt water) sailboat disintegrates while you're looking at it. A sweet water boat a bit less fast but still quite fast. GP has it right: the maintenance is where the work and the money goes. The proverb is "a boat is a hole in the water that you throw money in".
At least with a house the timeline is long and it's easy to hire someone to do it for you. Even galvanized pipes last 40-50 years without much problem, and newer pex pipes may last indefinitely. Roofs are 25+ years.
Absolutely. I once looked at an apartment on IJmuiden beach, it was only a few years old and it looked as if it was 50 years old (and had not been maintained in those 50 years).
I don't get why US houses are still built with shingles, they don't seem to last at all. Our houses are generally built with roof tiles (not mine, I've got a flat roof which will need to be redone every 25-30 odd years :/ ) which last for decades and generally only need a few replaced after heavy storms, maybe cleaned up if they look grimy.
Pipes are made from plastic and last decades, but they're generally not too hard to replace though.
I'd argue the biggest maintenance jobs to a house is keeping everything clean, basically the same as a boat. The other one would be painting every couple of years, and of course garden maintenance.
When I lived in southern California, roof tiles were very common but in the eastern US, it's mostly shingles. I hate to think of what a hailstorm would do to a roof full of tiles. Hail can cause significant damage to a shingled roof but it's much less expensive to replace.
Boats also have critical systems such as engines that need maintenance and despite that break often. Esp. on a sailboat, there's nothing more important than the engine and these are usually cooled by salt water.