The situation you describe sounds like it involves issues that go beyond the Web site itself. There are advantages and disadvantages to each of these forms of business organization and you need to be working with an accountant and a lawyer to sort these issues out. As an example of just one of these concerns, consider your revenue sharing from advertising. It very well might, which means not only that certain default rules govern how much of those profits you will share, but also that you will likely be liable for the errors and omissions of all the partners. This can be a tricky situation, which is why I recommend that you get legal counsel to work with you.
Legal fees can be fairly expensive.
However, not having adequate protection for your Web site, your partners, your company, your intellectual property, and so forth can be far more expensive. While I am not giving you any legal advice, I generally advise my clients to have at least three layers of protection from liability. Second, I recommend that they disclaim as much liability as possible through solid contracts. Third, insurance is a must. There is no point in accepting risks that one can insure against.