What Are Private Label Rights?
This is the one that needs to be read very carefully. Different people have different views on what Private Label Rights mean. There are two basic forms of PLR they are limited and unlimited. If you are lucky enough to get unlimited PLR it means exactly that. You can do as you want with the product you have bought, although unless you change the product substantially you should not think of claiming copyright to the product. Apart from that do as you wish with it.
Far more common is the restricted PLR licence. The restrictions can vary from one seller to the next even for the same product. Many restricted PLR products allow you to carry out any changes you wish, but you are not allowed to pass on the ability to change the product to your buyers. This in effect means you are selling the product with master resell rights.
As I say with any PLR product make sure you read the licence details in their entirety.