If you can get a good product with resell rights, a lot of the time the quality is really bad.
If you sell something that is of bad quality you are leaving a lot of repeat business on the table, and opening yourself up to getting a high refund rate. That is why I have written all of my products by myself.
If you release a good product then it can make you a lot of money down the road.
Here is my process:
1. Learn / Understand
2. Implement / Test
3. Write (using the 4mat system of writing) / Proof Read
4. (optional) convert to other formats (video, audio)
You won't go wrong with this method, it might take longer but its worth the effort.