Well, I've never had "white" hair (platinum blonde is the lightest I've ever gotten), but really, it's just hair that's been bleached to light yellow and then a toner has been applied in order for the gold tones to be neutralized.
The problems with "white" hair...
1. Sometimes difficult to achieve the light yellow color of the bleached hair. If your hair is dark, bleaching it to a pale yellow may be difficult or nearly impossible.
2. When you have bleached hair, your roots show almost immediately. It's a pain that you learn to deal with, but basically, you must touch up your roots about once a month or so (toward the end, the roots will be nearly unbearable, if you're anything like me - I hate dark roots showing!).
If you do it, just be prepared for some upkeep. It can be really great to have light blonde/white hair, but it is a lot of work. It doesn't have to cost a lot of money, but you will need to purchase bleach and toner and may need to experiment with some different brands of toner in order to find the perfect one.