If you are serious about purchasing a franchise, you will be given a copy of the franchisor's Uniform Offering Circular (UFOC), which contains financial and material information about the franchisor. It's smart to hire an accountant or a franchise attorney to review the UFOC and financial statements.
This professional service may cost anywhere from a few hundred to several thousand dollars, but it's a wise investment given how much you stand to lose if something goes terribly wrong.