amfoto1 wrote:
In addition to KEH and B&H, Adorama's used dept. is good source, too. I've also bought used stuff from Henry's, in Canada.
Depending upon what you are seeking, you also might check the manufacturer's website for refurbished. Those can be a good deal, too.
I have purchased three used lenses from B&H. The first one I just did not like, not sure why, but they took it back with no issues. The next two were great. The Nikkor 18-140mm I bought is my 'stay on the camera', everyday lens and does a good job for most of what I shoot.