I found a couple of listings for Trek bikes being sold on Craig’s List. Putting over $100 into a bike is kind of scary. Not really knowing what I should be looking for — also scary. Will it fit? Will it ride well? Will I like it? Does having 9 gears versus 21 gears mean it’s bad? Or is it 9 gears front, 3 gears back? Road bike that’s lighter versus hybrid that’s heavier? Will I ride it as much as I think I will?