Wall mount vanities are a very big trend. They are for the contemporary home with sleek styles and finishes. If you have a contemporary flair and remodeling your bathroom, a wall mount vanity will make a big impression. Since there is no bottom to the vanity it makes it really easy to clean as well. It sounds like an easy decision to make if you like the style but be forewarned. It may cost a lot more than what you may expect.
The installation of the wall mount vanity is where the cost can go up significantly over a floor mount vanity. Before making any purchase, discuss the costs with contractor so the expense is known upfront. Many contractors have never installed a wall mount vanity but they'll tell you it's no problem. It's not unexpected to question your contractor's experience. If they have no experience, later they may come back to you with "unforeseen" issues and demand more money. It is important to discuss those details before the purchase is made and even then there still may be something "unforeseen". This is unfortunately true with most aspects of the renovation process.
There are two main issues to address with your contractor when installing a wall mount vanity. First, discuss the installation to the wall. Since you will not have the vanity yet, you may not know how it's supposed to be installed. There may or may not be installation instructions available in advance or at all. This is more common than you may think but the industry is starting to provide more information overall. The installation is more about the wall and the stud and less about the vanity itself. Reinforcing the entire vanity wall before tiling is widely recommended. The vanity is normally bolted to the wall. Second, be sure to address the location of the plumbing supply lines and drain. Many wall hung vanities have a U-shaped cut-out to accommodate the drain. This is especially common for any vanity with drawers in the center. The supply lines and drain need to fall within the frame of the vanity and they must be centered if there are any U-shaped cut-outs. If the vanity is open on the inside without shelves or cut-outs then the plumbing does not have to be in the center but it is more visually appealing when you open the vanity doors. If you will need to move the plumbing to accommodate the vanity, please discuss the additional labor costs before you purchase the vanity.
By addressing these two major issues with your contractor prior to your purchase, you will clearly understand the total cost involved with purchasing a wall mounted vanity. If you are doing new construction, you will still need to review the vanity specifications with the contractor.
Good luck with your renovation and wall mount vanity purchase!