Proz.com is a site where you can get paid to translate all kinds of documents, including files and even conversations. The site provides you with an opportunity to list your services as a translator. They offer opportunities in Spanish, German, Italian, Chinese, Arabic, Japanese and other languages, and specialize in legal, medical, technical and other fields.
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.