The big advantage with selling private label ebooks, is that it’s a very fast way of getting a product to sell, with very little effort and in many cases with very little outlay.
However, the drawback of this is that potentially many other people could be selling the exact same ebook as you. Before you jump head first into completely re-writing the ebook adding to the content of a PLR ebook, you really should test the market first, to see if the ebook will sell first. Once you begin to see a few sales coming in, you can then look at ways to develop the original PLR ebook, into a much better and completely unique product.