It's been a while (a very long one) since I did partnership stuff so my memory may be a bit hazy, but regardless of that the fact still remains that if the previous owners have lied about material issues then the new owner would be well advised to put a lot of effort into establishing the exact situation on the ground and not rely on anything the previous owner had said.
If the business was a limited company. would the new owner not be liable for the debts owed by the company ? I know the original poster said it was a partnership, but someone who has an employee off the books might also be liable to say the business was a partnership of that suited their purposes. I know the buyers accountants should spot that kind of thing, but you might also expect them to spot someone being employed off the books.
My main point remains - the new owner should put a lot of effort into being absolutely clear about the state of the business as soon as possible.
z