The idea of a "PT" has been around for some time. In particular, Scope International has been selling books on the idea. While in the past few people have had the type of work that would permit this life-style, technology is making such work more common. Many people have left places like Silicon Valley for places like the Colorado Rocky Mountains, and now telecommute to work. As the Internet keeps growing, and satellite phones become common, more and more people will be able to work from anyplace.
In the past, most people could not afford a large yacht. Today, such a "world mobile home" is not really more expensive than a home that does not move. For example, the 65 foot long sailboat the MacGregor 65 was about $150,000 new around 1994 (they no longer make it). This is a good price, and that is probably why they can say "best selling large yacht in history". One family, or two couples, could be very comfortable on a boat of this size. It will do over 10 knots under power and 20 under sail. A used one, or one without sails, should cost even less. For a real live-aboard, you will want to add a few things like an air-conditioner, a water-maker, and a washing-machine. MacGregor (714) 642-6830 made a couple more in 1999 for the owners.
After the 3 to 9 months that a country will let you stay, you can pull up anchor and go on to another country. At 250 miles per day, it would not take long to get to another country, especially in the Caribbean where some island countries are 20 miles apart. If you are going to be working anyway, and are not in a hurry, a slow yacht can get very good gas mileage.
Boats cost a bit more to operate/keep-up than a house, but they do not have property tax. In PA the property tax is about 3%. For a house as expensive as the MacGregor 65 this is $4,500/year. Note that with social security, self employment tax, health tax, etc, a person inside the USA needs to earn more than this to have enough "after tax" money to pay $4,500 property tax. If you only move the boat 4 times a year, the annual operating costs should be less than this. I have been told by real live-aboard sailers that the costs of maintaining a boat are not much higher than that of maintaining a house, it is just that on a boat you can not defer maintainance costs. Boat repairs all need to be done right away to keep the boat as safe as possible.
You can get a mortgage for a boat, so you don't need to save up forever first. Also, if you live on the boat, interest payments on the mortgage are tax-deductible. If you plan to become a real "PT", tax-deductions are only an issue for the first year.
For extra money, you can always rent out a room on your boat. Strange as it sounds, it seems you can charge more for the rent of one room than you would be paying in mortgage payments for the whole boat.
If the country you currently have your citizenship in decides to try to "close this loophole" then you can easily renounce your old citizenship and get a new one in a more reasonable country. I don't have anything online, but the back of "The Economist" has ads by a number of companies that will help you buy a new citizenship.
So with this type of life style, one need not hassle with social security tax, income tax, health tax, property tax, investment taxes, etc. On top of having far more money and freedom, you don't have the paperwork!
There is a live-aboard list for people that either live on boats or want to. Send mail to email@example.com to get added.