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.
When creating a membership site, always offer different plans and pricing tiers to appeal to your different categories of audience. Access to specific types of content is then dependent on the plan selected by a member. Membership fees can be a one-off payment or a repeat subscription. And you can even sell products on your membership site to boost your income.
To make money fast, you should apply to all the relevant tutoring positions available on the websites below. However, you should also outreach to university and college websites and student forums. For example, McMaster University has a student forum called MacInsiders. You can reach out to the university forum for your community and let them know that you’re willing to tutor students. Reach out to students in your local community about tutoring opportunities. 
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.