Subscription to stocking site and get copyrights to use at any producd


Good day …
I have a question about Copyright Rights…
I am going to Buy a Subscription Some Stocking site and they have Providing Rights to use there Contents (Graphics, Text, Video etc) for any commercial and for perusal use,

So my question is that,
if i use there contents for my client at any project so it will create a copyright issue for me or not,
if the client got copyright issue for the contents so how i will provide him a proof that i have Rights the contents to use an any project,

I need information and guidenes for this ,