For me it depends... If I need to make room I've sold them as young as two weeks old... If I have plenty of space I like to raise them as long as possible... That way I know the ''customer'' will receive a gecko that is eating heartily and is sexable...
I don't plan shipping until they are 20 grams or more. I'd probably sell one locally at 14+ grams. I will list one for sale that is small, but I won't ship it out. But it can technically be sold before that size.
I prefer to wait until they're 15 grams which I don't think happens earlier than 6 weeks or so for most geckos. I'll sell earlier to an experienced person under certain circumstances.
We planned on waiting until the geckos were at least 20 grams, but with the weather being far too hot for shipping anyway, our geckos have gotten to be 30-40 grams, and we have found that we prefer them to be this size before selling Although for a local pickup, we have sold a gecko as young as 10 grams, which was about 6 weeks old; and the person was also experienced.
It depends on the morph and the individual gecko, but I like to wait until they are around 20 grams. This will usually confirm the gender, and give an idea of what the gecko will look like. More than that, it is well-established and somewhat tame!
10 or more grams works fine for me in many years of shipping. I have great system for acclimation my customers use. If I am waiting for a morph to develop I may wait longer. If I am not sure about the morph turning out I price accordingly lower, if I sell them before you can tell for sure.
The last years 2-3 Months or 15 g was the minimum I was selling them.
This year I wait until they are 4-5 months old or 25-30g. I just like to see how they change! And with colour morphs I think its better for the customer when they are a little bit older because it's easyer to say what colour they are (Hypo / Super hypo / Sunglow ) or for example if the snows become yellow.
I would wait at least until they are 2 Months! So you can determine the sex (when you are experienced) and you can watch them grow!
We try and wait until 20 grams. I had a couple that were 15 and 17 grams that I sold to people that I knew real well and knew they would take great care of them.