When doing basic estate planning, one of the most important instruments to set up is a Last Will and Testament. This allows you to designate beneficiaries, i.e. who will receive your estate assets. The Will also designates the Personal Representative, i.e. who will be in charge of your probate estate. [Note: in some states, this person is referred to as an "Executor" or an "Administrator" but regardless of the name, they are essentially the same position.]
When buying a business, you more than likely purchase all of its assets as well, in order to avoid duplicating your efforts. In addition, you also purchase its goodwill and intellectual property. Valuing those assets is not as easy as valuing inventory, however.