I would recommend buying a few of the books by Nolo Press on taxes and business structures for small businesses. Even if you just look at their web site they have a lot of the basic information there for free. They have a book just on partnerships which is what I think you have now, but ideally it is usually best to have a business structure with limited liability. That way if you get sued your personal assets are generally not at risk.
Buying several of the Nolo Press books was one of the best investments I made when starting my business. Plus the cost of the books may be tax deductible.