Starting your own business on ebay or Amazon can be very lucrative if you approach your business in the right way,
The most successful people in Internet marketing started with ebay until they found their own niche.
Virtually to Man the big problem they all found was the time consuming side of posting and packaging Daily.
For a while I was selling Antiques and Books at ebay and Amazon respectively and even though reasonably successful I found this the biggest problem was continuously collecting boxes and bubble wrap from a friend's relation and anyone who could help.
A similar problem with Amazon was the postage fees.
I will address both of these problems individually which may help those considering starting their internet businesses in this direction
If you are just starting and looking for a niche to sell in assuming you are not just emptying your home I would look for items that are of regular size and shape that will easily fit into readymade packages which can be bought over the counter, there are various sizes available that not only make life easy but also will look very professional to your clients, presentation is very important in any business and to unwrap any item from a shoe box will not give the best impression.
If you are selling items from your home this is acceptable but definitely not be you are looking to enter into a professional niche.
When selling on ebay you are responsible for setting your own postage costs and the correct price for competently well packaged items will be acceptable and leave the a good impression
With Amazon there is a slightly different problem in that Amazon have a preset price structure for posting, with this in mind I would suggest that you become very aware of the cost that each book will cost prior to setting a selling fee.
There are thousands of books on sale at Amazon for only 1p and it is possible to make a £1 profit through postage costs not a bad profit if you could buy enough books at the right price and sell on quickly, this unfortunately will be very short lived just through the boredom alone.
Be very careful if buying books to sell on as some very large and heavy books will cost far more to post than Amazon pays, so be very aware of size and weight before any purchases.
Again opening a book of a protective envelope will leave a good impression.
To beat the stress factor of continually wrapping boxes of irregular shape enter a niche where your products are very similar in size or can fit into the packaging that can be bought and with books learn postage cost if the profit on your book is very small.