7-10 years in most states. But...its really hard to do cause all the owner has to do is walk in one time during that time period and you're out. So if you find a hunting cabin out in the woods you might be able to pull it off if the owner doesn't visit for years, would probably still be a sticky legal battle because property rights are sacred. But if you're trying some where populated any time the cops come through it resets your timer. Oh and as for a paying taxes I'm pretty sure you don't have to pay them until you officially claim it as your own then you pay the back taxes.

In rural areas away from subdivisions its might be easier. It just puts you way far away from "services" and "work" though.

There always some old barns or a mobile home or car parked in the middle of a pasture for 20+ years that nobody pays attention to daily. Probably have to keep moving somewhat frequently and keep a low profile at the campsites, there are hunters out during hunting season and folks checking on their cattle to avoid.