You can, but I cannot stress enough how much of a bad idea it would be not to incorporate from the very beginning. Also, you should not wait to obtain legal counsel. If you go for it alone, you could miss some nuances that have a direct impact on your business. For example, the type of corporation you decide to establish will impact how your startup is taxed and whether your personal liability is at stake. A lawyer will be able to advise you about the ins and outs of incorporating as a limited liability company (LLC), S-Corp, C-Corp, or as some other type of corporation (more on the various types of corporations here). You will also need to give careful thought as to where you incorporate your business because not all states are created equal--some states are very friendly to startups (think Delaware) and others are considered less so. An attorney will provide you with expert advice about the pros and cons of the states you are considering for your company.
Forgoing obtaining a lawyer at the beginning stages of your startup could cost you a lot more money down the road if things go wrong. The good news is, obtaining a quality legal professional at a reasonable price is not out of reach, even for a new business.