Buying used isn't a big deal, a lot of cars are sold used with no issues, in fact that's all I have ever bought are used cars and never have problems, the same is true with the bikes. Over the last 40 years I've bought 4 used bikes, all but 1 of those bikes I still have and use, in fact one of them is my main touring bike! The one I don't have I gave to a friend who still uses it and never had any issues. Let me tell you something, when you're touring you don't want a worn out piece of junk, my touring bike was 100% original when I bought it used and still is till this day. What's really weird is that I have found 2 bikes in dumpsters, one I gave to my youngest daughter, and it has never had an issue, the other is another touring bike that took a lot of cleaning to get some sort of unidentified sticky blackish goo off of it but now looks and runs real well and I would think nothing of it taking it on a long trip.
Besides that what happens after you buy a new bike and you've ridden it? It becomes used! I still have and ride a "new" bike that I bought in 1984, it has over 150,000 miles on it, and I don't even think about it possibly breaking on a ride, of course I don't ride that bike far or as much as my newest bike which is a 2013 I bought new that now has about 8,000 miles on it. Geez my main touring bike I bought used has less miles on it then my main road bike!
There are lot of people who buy bikes with the good intentions of riding it, which they do for about 3 to 6 months putting about 250 to maybe a 1,000 miles on them, and then it sets in their garage till one day, who knows how many years down the road, they decide to sell it in a garage sale. Those are excellent bikes to buy. One of the used bikes I bought about 5 years ago only had 5 miles on it since it was purchased new in 1984! This bike was so new the rear derailleur wasn't even broken in yet! My main touring bike only had about 250 miles on it when I bought it; the touring bike I rescued out of a dumpster I'm not sure but it looks to have all the origina stuff including ring gears and rear cluster so I'm thinking with the little wear on the gear cluster it has between 3,000 to 5,000 miles on it, and the ring gears still look new.
Anyway long story short, I would never shy away from a gently used bike for riding because a lot of those bikes will have less miles on them then most bikes that were purchased new by people here on this forum are riding. Scared of buying a used bike? you shouldn't be. If you're not sure what to inspect on a used bike to see if it's good ask here; the one thing I would strongly recommend against buying used is a carbon fiber bike.