Hi rmwolfe,
As I understand from your email, you are intending to buy a spa business that is already in operation. This kind of transaction would need to have documentation to support the sale of the business and the transfer of assets or properties used in the business regardless of whether the seller (original owner of the business) is a corporation or a sole proprietor.
Nevertheless, the manner and type of document to be used for the transfer of the business may vary. In this case,it would be necessary to determine the status of the seller and how you would like to go about with the transfer.
-Atty. JB