You've only got the seller's photos (usually bad ones), description (usually vague), indirect answers to 'pointed questions', and probably most important the reputation of the seller, to base an online purchase decision on. That covers overall structural/cosmetic condition of the instrument; but as for tone / volume / playability /mojo, etc you have to take a leap of faith anytime you buy before you try.
My personal experience having bought a bunch of acoustics over the net, has been about 50/50. Some keepers, some sleepers...
My current 3 Taylors I had the luxury of playing before buying, and they seem to be keepers.
