Actor Michael Caine says the best financial advice he ever got was to own something that makes money while you’re sleeping. In his case, it was partnerships in restaurants. Lucky for him, they were successful restaurants. Owning one is also an excellent way to lose money while you’re sleeping. You have only so many hours to work each day, so the best side-hustles are things that don’t take up much of your time. My eBay business was cutting into my writing time to the point where I had to scale back.

My most lucrative side-hustles have been investment in comic books and stocks. My husband started his collection in the 1970s, so my success is mostly luck because he bought super cheap all the key issues people are drooling for now. We’ve sold comics for thousands of dollars he bought for 25 cents brand new.

Side-hustles are simply an attempt to put multiple income streams in place. I know this guy on Long Island who’s a genius at it. His job is selling medical supplies and earned enough to buy a nice, four bedroom home. He’s single and so can be flexible about his living space. He rents out space on his very long driveway to people who need to park their cars somewhere, uses a basement apartment for Airbnb, and rents out a couple of rooms in his house. He’s saving up to build a second home on his property so he can rent the other one out and ditch the roommates.