One thing that I was taught to do with all my PLR is to take stock.
PLR is great raw material, if you're willing to redo it.
Also, when you can pay MORE for PLR, you're typically getting something that when you redo it, you can have a quality product.
So my two main rules are:
1) Pay for high quality,
2) Buy with the intention of creating products (not just selling as is)
3) Be willing to re-do it.
Typically, when you buy business opportunity or make money online products, you can use and re-use the content in a number of ways.
This kind of puts you in the product creation game.
But you might be saying, YES, but everyone has the same package.
Not if you redo it; not if you're trying to solve problems in the marketplace; not if you're wiling to become a product creator.
When you add in case studies, you've made PLR unique.
When you add in personal experiences, you've made PLR unique.
I have some more tips, but this will get you going.