To begin with, tourism didn't really exist in the Middle Ages. Without a doubt, people in the Middle Ages travelled a lot, be they defeated Anglo-Saxons travelling to Constantinople to serve in the Varangian guard, Franciscan friars travelling to Karakorum as emissaries for Louis IX of France to the Mongols or just peasants going off to sell their produce at the market fair 8 miles away, but travel in those days was always in some way connected to politics, religion or business. Tourism in the modern sense - travelling to places beyond your normal area of work/ study for the sake of personal leisure or cultural enrichment, began in the long 18th century (c.1660 - 1830) when young aristocrats, as part of the completion of their education, would go on "The Grand Tour", theoretically of Western Europe but mostly of Italy given how much education at that time revolved around Classical Rome. Not unlike the modern day Spring Break, there was a huge element of sexual libertinism and just generally having a laugh and a good time to it too. Around the same time, the first seaside resorts developed as 18th century doctors believed that seawater contained certain health benefits. With the advent of railways and steamships in the 1840s, and the creation (around the same) of the first travel agencies like Thomas Cook (1841), tourism began to become available to people outside the aristocracy and the wealthy bourgeoisie and so one can start to speak of mass commercial tourism, though certainly nowhere near the scale of today.

Turning back to the crusader states, vast numbers of people travelled to the crusader states not to fight. Simple religious pilgrimage meant that by the third quarter of the 12th century, people from all over Europe and beyond were flocking to it - John of Wurzburg, a German who visited Jerusalem in 1170, describes how there are “there are Greeks, Bulgarians, Latins, Germans, Hungarians, Scots, Navarrese, Bretons, English, Franks, Ruthenians, Bohemians, Georgians, Armenians, Jacobites, Syrians, Nestorians, Indians, Egyptians, Copts, Capheturici, Maronites and very many others.” As is well known, merchants from the Italian maritime republics of Venice, Genoa and Pisa would travel to do business at the ports of Tyre, Acre and Jaffa where they had special designated hostels (modelled on the Islamic funduqs) and even trading colonies. But travelling to the Holy Land was not easy. If you were say a French nobleman on a pilgrimage, you would need to place your lands in trust with a local bishop or monastery, lest your neighbours or relatives try to take it off you in your absence, and probably sell some of them to make the money necessary to take the very expensive journey. If you were a merchant, then you'd need to find an investor in your city to provide the capital in return for half of the profits when you returned (it was through journeys like this that the share-holding business partnership developed). When you were actually making the journey, you'd rely on the Knights Templar to keep your money safe - you would deposit money in your local Templar chapter, carry a bill of exchange with you on the journey and then collect the money from the Templar chapter at your destination (this was how cheques were born), and for accommodation the Hospitallers could be relied upon (their hospitals provided food and beds to pilgrims free of charge).

Books you might be interested in

"Jerusalem in the time of the Crusades" by Adrian J Boas

"The Routledge Companion to the Crusades" by Peter Lock

"An economic and social history of Later Medieval Europe" by S.A Epstein