People are turning to audio and visuals when it comes to technical subjects. However, you should consider doing an ebook first and turning it into an audiobook through a resource like Audible's ACX platform. You can hire a producer either through a royalty share program, so you don't have to shell out upfront cash, or you can do a pay-per-hour hire as well.
I wouldn't think of a high yield savings account as a source of passive income but your savings should be getting something (less like Seinfeld syndication residuals and more like a commercial jingle residuals!). It won't make you rich but it's nice if your baseline, risk-free rate of return on cash is 1% or more. The best high yield savings accounts (or money market accounts) offer higher interest rate and there is absolutely no risk. CIT Bank currently leads the pack with the highest interest rate.
Did you ever see the movie Stripes? It's an 80's classic and one of those timeless comedies with Bill Murray. Click here to see Harold Ramis teaching his English class the Do Do Run Run by Shaun Cassidy. To get started teaching English as a second language to adults, go through your local schools and colleges to find classes where teachers of English are needed.
Fiverr is one of the biggest providers in the gig economy on the web and you can sell a wide variety of services and products through this medium. Do the research and find out what you can offer. However, keep in mind that like any other money-making task, it takes time to succeed here. And stellar reviews will help you generate more and more income over time.
Another option: Consider starting your own real estate investment group. This is a great way to team together with other small investors, either via pooling your money together or simply by learning from eachother. According to Joseph Hogue, CFA from PeerFinance101.com, “The common bond in all real estate investing groups is that you help each other compete against the big money players to get the best returns.”
Using a food delivery service can’t necessarily earn you money, but it can help you save you money if you constantly find yourself throwing out half the food you buy. Food delivery services send a box of food every week with new, sometimes unique vegetables, meat, fruit, and so on. If you don’t have time to shop and want simple meal-prep that leads to a good meal, a food subscription service may be perfect for you.