Sellers tend to inflate their position.
It is during the due diligence time that the buyer can actually verify what the seller has said. Usually, the buyer has a right to fully check the books and other important documents such as leases. Further, if during the due diligence period the buyer finds things were not as suggested by the seller, he or she can exist the agreement and get their deposit returned.
The above seems simple enough but it speaks to the need for all kinds of support people to do "due diligence" properly. Most likely the buyer will need a accountant, lawyer, business broker and common sense to get the job done.