Yes, I had a store on eBay for near three years. I reached both a Bronze Star level and was a Top Seller for over a year before closing the store. It was a niche market for NHRA drag racing memorabilia. I may open a new store again once I know a few more things. It will still have that niche market, yet I will expand to other mainstream items as well. Not sure how yet or what.
I did begin by selling odds and ends from around the house that I never used or had extrinsic value based on my investment. Once those were sold off, then I marketed those with a variable intrinsic value determined by the bid. Profit is not necessarily the goal as much as receiving a financial gain at some level of a distressed item holding no personal intrinsic value or at least chose that avenue of opportunity.
All in all I think eBay is a good pathway for increasing cash flow, obtaining a value with ease of marketing to a wide market place rather than a narrow neighborhood or community, and opening doors toward other opportunities - learning their system, making friends or network opportunities that can be used even here at HP, and more too.
For example if the niche writing market is complimented by a niche eBay store more opportunity occurs. If those windows of perception become doors of reality one may feed the other and an alliance may be formed benefiting both parties. If you are both of those parties then there is even a greater benefit.
If you write about toddlers and sell home made custom toddler clothes for instance on eBay opportunity exists. If one knits while writing articles and becoming an expert on knitting, then the intrinsic value of the products made by you increases at your store. You have the opportunity of backlinking from eBay and choosing the (Or, your store) at the article too. A little thought and many windows may become apparent. The doors will lead to the what, where, when, why, who, how, and how much while adding maybe how long as well.
Oh yeah, that could be done with Amazon as well. Just different . . .
Like HP there is a learning curve for the costing factors incorporating the fees at eBay and/or Amazon. eBay may be easier than Amazon, although I am not sure since never marketing at Amazon.