I second Alexandra’s suggestion that legal expertise can be pretty crucial for your startup.
Having a lawyer from the very beginning (incorporation) can be helpful. Some people think incorporating a business is only a matter of filing some paperwork. While you do have to file paperwork, there are other things to consider and take care of when forming a business. For example, how you incorporate will impact the way your startup (and yourself) is taxed and whether you have any personal liability if anything goes wrong with your business. A lawyer will be able to advise you about the ins and outs of incorporating as a limited liability company (LLC), an S-Corp, a C-Corp, or some other type of business form (more on the various types of entities here). Because not all states are created equal--some states are very friendly to startups (think Delaware & Wyoming) and others are considered less so-- a lawyer can also advise you about the pros and cons of incorporating in your home state or some other state. Having a legal adviser will also be important if you ever want to change your corporate structure or expand your business into other states.
In addition to incorporating your startup, an attorney can assist you with a number of other legal matters such as helping you secure and protect any intellectual property rights for your startup, drafting key contracts and agreements, and advising you on tax matters.