Shipping. You will only have a few days to ship a book after it sells, and even less time if you agree to include two-day or overnight shipping as part of your options. And since you’ll want to save as much as you can on the shipping, you’ll have to devise a plan. Many people set aside specific days for shipping – say 3 days a week – and then make one big trip to the post office. As long as there isn’t anything else in the package, you can send books via media mail, which is the least expensive option. Finally, your books will need to be packaged in a way that they won’t get damaged in transit.
If you have a good idea for an app, and the skills to create it, then producing your own premium app can be profitable. However, with so many free apps available, it may be hard to convince people to pay. If you want to go down the premium app route, consider having a basic free version to encourage people to download the app in the first place. You can then provide the option of upgrading to a premium plan once users realize how useful the app is.