First of all, you will need to do your research.

This is true with any business.

You can do a fair amount for free and there are link on the side that will allow you to do some research for free.

I will also post here some tips.

Use the completed auction feature inside each sellers listings. This will tell you a finite amount of info on any given seller.

Ebay allows a limited search to be done on any seller, after this you must pay. If you want stats going back a month it's free. If you want longer than that you will need to use a service. Terapeak is pretty decent and they have a easy to use interface.

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