Marketing. When operating as a consultant, you won’t necessarily be marketing your company; you’ll be marketing yourself. You’ll have to “package” yourself in a way that makes people trust you. For instance, if you’re marketing yourself as a financial consultant, ask yourself why someone would trust you with their life savings, and then figure out a way to convey that to potential clients. It might be in the form of a brochure, a portfolio, a sales letter, or all three.
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.