AirBed and Breakfast will definitely appeal to younger travelers, and conventioneers who can’t find a regular hotel room. In overbooked Denver, where 20,000 people will be descending for the Democratic National Convention, hotels are already sold out. More than 600 people have found alternative accommodations through AirBed and Breakfast, and 50 to 100 new listings appear every day. Prices range from $20 a night for an airbed to $3,000 for an entire house.