Bicycle touring requires many types of gear. Between purchasing a bicycle and all of the gear it can add up to a significant investment, especially if the investment isn't stretched out over a period of time, piece by piece, and if the bike and other gear are new. If it all comes at once, the price of a bike and the gear can be a little overwhelming. But for anyone that is interested in taking the time to learn how to be a bit resourceful, both a bicycle and a unique, highly effective gear-carrying system for all of the essential touring gear for high-performance, long-distance touring is available with a relatively small expenditure of dollars and a small amount of simple fabrication.
I've taken many tours in which I have embarked with only a rear pair of panniers. Later, when I traveled into areas that were off the beaten path a bit, and I was forced to take additional food and water to allow me to travel between widely spaced points on the map, I'd shift some of my gear to the front of my bicycle into stuff-sack panniers that I'd made. The stuff sacks are very tightly fitted (strapped) to narrow, vertically mounted platforms that are quite solidly attached to the sides of my front rack. The combination of featherweight stuff-sack panniers and platforms provides an extremely effective gear overflow system. Through many years of experimenting with different stuff-sack systems I've been able to come up with ones that are both superbly stable and astonishingly lightweight, and that are quite easy to fabricate. I've adapted the overflow systems into rear stuff-sack panniers / platforms as well.
If you can sew a stuff sack, or are willing to learn how, you can easily create a system that will be vastly superior to any of the dry-bag type panniers on the market. Your panniers will be dry and they'll be dramatically more stable at about 1/6th or 1/8th the weight of the commercially made panniers.
I find that one of the key components in transforming an inexpensive used bicycle into a dynamic touring bicycle lies simply in being open to possibilities, and in being able to recognize potential in a wide variety of bikes. For a hundred bucks to purchase a used bike and an additional hundred or two or three to modify it, a touring bicycle that will widely out-perform any new $10,000 touring bicycle, that I did not build, is easy to create with a little resourcefulness.