Well based on my experience, I can say ecommerce marketplace like Amazon, eBay and Etsy can earn you profits quickly. The best business model would be print on demand. You can join platforms like Redbubble, Amazon Merch, Etsy, Zazzle, eBay to sell print-on-demand products. To generate quick sales you will have to do SEO and run ad campaigns.You can also make quick profits by selling digital products. If you're unsure how to create products, there are numerous free tutorials available online to guide you through the process.