Selling your own digital product is an excellent monetization method. That’s because there’s no middle-man between you and the buyer that’s taking a 'cut’ from the possible income. This approach seems to be fairly straightforward, unfortunately, it’s not that simple in reality. Creating good product require a ton of time and additional resources (like design, content, etc.). There’s a lot of ‘hidden costs’ as payment gateways, shipping, and taxes.
Now, when you know how theoretically it should look like, it is worth to figure out what you can sell. It can be audiobook, eBook – choose what are you capable to create and it’s related with your site. Please also keep in mind your audience and give them content which they need and would like to pay for.