[Q] What visa can I use to enter the U.S. to take a look at a business I might want to purchase?

You can use your B1 visa or enter on visa waiver program to take a look at the business and do due diligence and purchase the business. Just in case you are questioned at the airport about the purpose of your trip, you should have a letter from the attorney, seller or agent stating that you are entering to take a look at the business and do due diligence, not to operate a business and receiving salary.