Suppose I was to purchase one of these container ships. Then suppose I was to anchor it off shore somewhere warm. Then I built a house on there, making boat trips to shore for supplies. Would I have to pay any taxes on my houseboat?
Could bring in loads of dirt, start a garden, more dirt, plant some trees...
I'll maybe let a couple chill people also come aboard, to build houses of their own... maybe.
It won't last long without maintenance at sea. Sea water is ridiculously corrosive to pretty much everything. If you want to live on a water, you better choose a smaller ship and put it on a fresh water lake.
Better yet you can stay on land and just build a hut somewhere deep in Russia. Russia has plenty of land where no human ever set foot, no one will ever find you. So you can live for free and do whatever you want. I remember reading Russian news a few years ago how geologists found a small village somewhere where people thought the country is still ruled by a Tzar. They missed Soviet times and Putin's regime, lol.
People have tried that, and failed for various reasons:
You can't move the ship out of any port without insurance
Insurance for a rusting hulk isn't cheap
No nation on earth will let you park your uninsured rusting hulk offshore, as it will pose an environmental and navigational threat to the area
Even if you anchored outside a country's 12 nautical mile economic exclusion zone doesn't mean their navy/coast guard won't bother you. They have maritime rights outside that area nonetheless.
You'd still need to take the ship in for maintenance somewhere, and now all your regulatory problems begin again.
The maintenance on the steel hull would require a return to territorial waters, at which point you'll need registration (read: taxes). The tender you use to resupply would also require registration and often insurance to enter into marinas.
You have to remain underway so if you can afford the fuel and maintenance, you can pretty much do whatever you want as long as you can defend yourself from hijackers.
If you try to anchor anywhere, you are going to be harassed or attacked by local militaries even if you’re in international waters.