[bobfirestone]

The biggest risk is you get something that is not what you want, are out some money and have to delay the launch.

If you are really concerned about it. A css framework can help your developer eliminate a lot of pain points and make a designers job easier down the road. For example twitter bootstrap is really easy to customize the color scheme, uses a grid layout, and does responsive design. If you don't like bootstrap there are a bunch of other frameworks that do the same thing.