Sure, it's really nice to be able to buy or build up a special 'touring' bike, but the reality is, 'if it's a bike, and in good shape, you can tour with it.'
My first tour was on an old 'first world war vintage CCM 28" men's bike, and although I had to replace a couple of crank pins along the way, it made the trip.
My first 2 extra long tours (1400-1500mi. each) was with an old rigid frame Norco Tango 18 speed that I upgraded with stronger axles, higher geared sprockets, high end derailers and shifters, and larger brake pads.(all which didn't cost very much) The bike performed very well, so much so that I will be using it for my upcoming 1000mi+ tour that's in large part on gravel and dirt wilderness roads. As long as it will handle a touring load, fits your body, and is in top mechanical shape, there's no reason you can't have an enjoyable tour with it.