You have an assignment due in a couple of days, but you are too busy. So you decide to buy your paper online. You pay for it$,$ make a few changes, and submit it as your own work. Have you done anything wrong?

No$,$ I paid for this paper, so it's mine. I don't see a problem with this.

How I "write" my papers is nobody's concern, as long I submit them on time.

Yes, I did. I am claiming this is my work, but in reality I didn't write the paper.