Don't tell me it's possible to do this with a YouTube video!

In trying to learn how to sidestep the arduous, for the uninitiated like me, process of creating my own videos in order to get started video marketing, I keep coming across the same type of advice: find a high ranking video in my niche, one that does NOT have any link in the description, and offer to buy it from the creator.

I gather to those of you with experience in the craft of video marketing, this sounds obvious and as easy as riding a bike. But, to me, it only serves to throw me off.

Supposing I manage to contact a video creator who is willing to sell me their video, how do I take possession of it? After all, it's not as though it can be mailed to my home, right?

I figure that, if and when, a transaction takes place, I would probably be given the seller's log in information to said video. Am I on the right track? But then, what would prevent the same seller, who already knows the access info, from logging in again and screwing things up on the channel, in one way or another?

Or, after purchasing the video, will if be possible for me to transfer it to my own YouTube account somehow (I'm not exactly sure about how), thereby protecting my investment? Is this how a You Tube video purchase generally work?

Any help or advice would be genuinely appreciated.