You definitely should be worried. There is a very real danger of your concerns becoming a reality. Your contract for purchase should contain a very well worded non-compete clause which will take the form of a non-compete agreement to be signed upon the actual closing of the sale. This agreement should be very specific about the number of years and radius of miles or geographic area of the non-compete. Also make sure the seller is signing both corporately and personally and that the agreement is transferable during the time it is in force should you decide to sell.