Things to consider when planning a barn wedding: additional lighting, a tent for the ceremony, professional company to clean the barn, seating, table, service ware, linens, and food if not provided by venue. If you are catering and having professional entertainment, consider their electricity and other setup requirements. Consider what condition you will leave the barn in and are you required to do any clean up (or perhaps its included). Keep in mind that your costs will depend on what is included and what you will have to add to make your venue the success you want it to be.
As a Barn Wedding Photographer we can tell you that each bride and groom have their own styles and there is no standard way of running a Barn Wedding. Other things to consider include managing the flow of people from the moment they arrive, to the journey to the ceremony, off to the reception and perhaps an after party. Will your visitors be walking over potentially muddy fields or are there paved walkways? Consider elderly guests or special accommodations guests. Are their bathrooms available on the property?