Like Resell rights, private label rights offer you the potential to take a product that is not yours and sell it and keep all the profit. The primary difference is that you can label the product as your own creation and modify it as you see fit.
Modifying the product will be relatively easy if it is a text based product, however audio and video products leave less room for modification, while it is possible the continuity of it will be not as great. Additionally with video especially it is kind of hard to hide the fact a different person is doing it unless you always have videos from the same author.
The primary benefit of private label rights though is that you can take an average product, extend on it and create a new product which you can sell for a high price. Or you can take a few products package them and again sell for a better price. Also combining products on a similar topic such as a short book (100 pages), with an Audio or Video Course, can expand your opportunities greatly.
One thing about private label rights though is that often they will cost you more, this is for two reasons. One the author is giving up the right to have their name on the product, and the second is that often distribution is to a more limited number of people, because the number of times that people see the same product with a different name on is going to only allow for limited opportunity.

