I thought the peak of my success with a "money-making" app was decluttr (every 50 dvds you scan, maybe 1 will be accepted for 12¢ a piece - I think I sold 100s of books and movies & made a tad over $100) or InboxDollars (every 6-9 months you get to cash out at $30). When I made my first sale on here I was skeptical, but 2 months later I've made over $1,000 :) You won't get rich overnight, but it's the best side gig app I've used so far, & highly recommend it!