Most people looking for zero taxes rent and don't buy. Real estate prices have doubled from 2003 to 2008 and have increased another 20% since then. One can rent a simple studio for about EUR 1'000 per month, including all the charges that comes to about $ 15'000 per year. A decent 2-room with some view comes to about EUR 30'000.
If as a trader you make >EUR 100k p.a., which would probably put you in the top tax bracket in you present country, you break even with living in Monaco. If you make more, you are well ahead.
Actually living in Monaco is not everybody's thing. Many have a nicer place outside of MC in France for everyday life. But living in the area is great; nice climate all year round, good food, lots of culture, lots of expats to mingle with and one can get around well with english language only.
Felix