If the bed and breakfast is service a real breakfast, they will have to have a restaurant or food preparation license. It should be located somewhere in the dining area and should be up to date and current. If the b & b is not providing a cooked breakfast but just a selection of bakery items, they may not need a license depending on local regulations.
Always ask how long the bed and breakfast has been in operation. Since they are family run businesses a bed and breakfast tends to either be a long standing business or one that is just relatively new. A b & b that has been open for a long time typically has lots of repeat customers and may need to be booked in advance.