The main advice I would give, is go slow and steady!!
I was made redundant earlier this year and, like you, had a brainwave to start selling on Ebay.
I saw a product that I was interested in, but there didn't seem to be any on Ebay so I thought I start selling it. Feels like I was the only one interested in it as I didn't sell any whatsoever and I was stuck with loads of stock. Thankfully I got them on sale or return so it wasn't too bad.
Now, I've ended up completely changing the whole product range. Because of my earlier experience, I just bought small quantities that I was sure would sell.
Even at that, my sales on Ebay are only starting to take off now ... 6 months later!!
Make sure you have a safety net while things are getting off the ground.
Be prepared for the initial "pity orders" (or curiosity orders!!) and then nothing for weeks on end!
Everything you need to know is on the Ebay forums. Make sure to read them & familiarise yourself!
Before you start selling on Ebay, buy a few low-value items in order to get your feedback up ... nobody will buy from someone with little or no feedback!
Don't just pigeonhole yourself into Ebay. Try other auction sites as well - Ebid is quite good.
And good luck. Initially its hard and confusing, but its great fun too!!!