dear jerry, i bought an entire new system buying mostly used. i bought my 2 used AF-S lenses from KEH. i found them fair & honest & best of all, willing to give advice. the lenses were in mint condition (nary a scratch) & i paid about 20% less than new (B&H). some nikonians advise buying grey market. i haven't tried that option. i would be careful on e-bay:know what you want, your price limit, what accessories are included, the seller's feedback, etc. on photo.net, there is an extensive list of mailorder outfits & ordinary photographers' comments on those to avoid & those who are 4 star. good luck & have fun! judy from now sunny northwest
Before you decide to pay KEH prices for a used AF-S lens, look into a grey market one. KEH has a great reputation, but their prices are often close to discount prices on new stuff.
At least you'll have an idea if the used price is reasonable if you check the options. For grey market, I recommend Adorama, Delta International and B&H. I don't have any qualms about going grey market from a reputable dealer.
Another option I'd suggest is Ebay. It's not generally the best place to be a buyer, since auction fever often gets people to bid too high. However, you can get decent prices if you set your bid reasonably. Always check the feedback before bidding.