The most common structures are LLCs, partnerships, and corporations. Choosing which to use for your business depends on several factors.
In general, a traditional partnership is not ideal for most people. For small businesses, the choice is usually between an LLC and an S corporation. Which exactly will largely be based on tax and estate planning situations. While an S corporation has some tax advantages over an LLC, somewhat rigid ownership restrictions exist, and those benefits are time-limited.
In general, an LLC is often the best choice, especially if you have a clear plan for growth, but the decision ultimately depends on the specific circumstances of the business and its partners. It is not a decision to make without consulting an attorney.