Question:
What necklace lengths are the most popular? What is considered "in" and what is considered "out"? Do different generations prefer different necklace lengths? Who buys the more expensive, high-quality necklaces? Is there much of a market for them on- line, or does this type of jewelry only sell in department stores and boutiques? What type of designs are the most popular --- the conservative designs that could be worn at work in a professional office or original, exotic designs?

Answer:
Generally the most popular length of necklace is 15". Young people will tend to wear them shorter and older ladies who do not want to bring attention to their neck will wear them longer. As far as what is "in", that can change often. I would suggest that you look at the national magazines to determine that.

Women over 30 tend to buy the more expensive jewelry. You can do research on eBay in the Designer Jewelry section to see what is selling and how much it is selling for. Designers with a name sell items for well over $1,000. Your reputation and following will add value to your jewelry.

You can use the designer section on eBay to determine the most popular designs. Look for items that have a large number of bidders. The same type of jewelry is going to likely sell for higher prices at boutiques and department stores.

First hand research is the best tool that you can have in evaluating a business opportunity. EBay is a good place to start but it tends to be a cheaper market. All in all, you can still learn a lot from information that you glean from eBay.