I would stay away from this! If you sell anything in digital format on ebay and the buyer requests a refund he will get it in no time.So,watch out!
Dear why buyer request a refund we sent him the credit in cheaper then SkypeI guess you don't know how ebay & paypal function. some of the user's are mean.
I suggest you look for some classified site & forum where the demand for such digital product's are high.
digitalpoint marketplace and blackhatworld forum seem to be good in term's of selling and buying digital prod.
Lo, audience in the last forum quickly raise red flag if, they notice any fishy thread especially, when such thread are associated with a new member.
Good luck