I sell on both Ebay and Etsy. Ebay's search function is much better and listings are picked up by google searches. Their fees are higher and customers tend to have more of a garage sale mentality. I've been selling there for 6 years now.
Etsy is for vintage and hand crafted items. The customer base is looking more for well crafted quality items than a bargain. I've been selling there for 2 years now. The search function brings up the newer listed items, so if you are selling items in a saturated market, you will get lost quickly. Listings last for 90 days instead of the 7-30 on Ebay though.
You would need to set up an account on both sites and verify your identity with a Paypal account. This process I believe took about a week. You'll want to download and print USPS shipping rates and familiarize yourself with them. If you've never done so before, buy an item or two on both sites to familiarize yourself with the process, as well as build a reputation. Start with US sales, but consider international as well. I would say that about 30-35 % of my business is international.
To be successful you need to find a nitch. Do some soul searching and ask yourself what you really enjoy doing the most. What are your talents? Now ask yourself how you can do that and make money at it. Research what's already out in the market and figure out how you can stand out. Working from home is the best and more liberating thing I've ever done!
The small business association is a great resource that is free through your state if you have questions about running a business. There's a ton to learn and I will admit I was intimidated by the whole process for a couple of months. What I do: I have a computer, a digital camera, a vinyl cutter, an industrial heat press, and 3 sewing machines. I cut decals and print fabric items, selling to a global market in an economically depressed area. I've never gotten rich doing this, but I make enough to live comfortably and still get things done around the house. It didn't all happen overnight though.
Nothing says you can't still write that children's book and sell it on Etsy down the road either....