It can work out, if you have the right product (and I wouldn't suggest high street clothing on eBay is the right product, unfortunately)
I started hobby "selling" my product on eBay just as something to keep my brain engaged during my second maternity leave. That was 2005.
"Selling" in inverted comers because I retailed at cost price just to see if anyone bothered buying. They did. Price rose buy the business wasn't paying enough for me to give up work for another 12 months or so.
I then had 2 glorious years with business booming and me thinking I'd hit the jackpot. I gave up work and dedicated myself to my own business as well as looking after a young family.
Then the 2008 recession hit...
Everything went pear shaped and you do need to roll with these sorts of blows as a small business owner.
I took the time created by the lull in sales to teach myself coding and how to create a retail website from scratch.
Now, 11 years after my eBay retail business started, I don't give any of my profits to eBay anymore, all business is done thro my website. It's a healthy profit, I reinvest regularly and my google rankings are doing well.
For now, my business isn't multi-million, but is enough to be able to be a SAHM to our 4 children and fit work around my children.
In terms of the OP, I'd find it difficult to take the risks needed in early business if I was wholly relying on immediate profits. I could only have successfully grown my business at times when it was ok if profits had fallen (because making changes might reduce profits just as it might also increase profits).