What Tourism is can be debated are hotels for example part of tourism or is tourism part of the hospitality industry? By the same virtue ancillary services such as banks may exist purely because there are many tourists in a destination. The business of tourism can be examined in many ways such as the motivation for travel and are divided into typologies - have a look at Plog's work on this.
Tourism can be short term trips or longer term trips - a day visit to Disney for example could be considered as day tourists but those who stay for a week or longer are also tourists. Industries impacted by the development of tourism such as schools, hospitals, improved roadways and transportation systems are arguable all part of the business of tourism. It would depend on the focus of the examination as to how 'the business of tourism' is defined. Good arguments can be made from a number of perspectives.