I, too, would probably avoid this boarder. If they still want to come see your facility after having asked that question, make sure you have them fill out some type of "boarder application". The fact that we have a boarder application scares off the people we aren't interested in having at our facility, anyhow! The sincere inquiries, from people who want the best for their horses and can afford it don't seem fazed.
Could you please tell me what is on an application? That sounds like a great way to weed out the less than desirables.