If you're not self-employed and work for a company, find out if they have a retirement plan. If you're lucky, employers will sometimes match contributions you make into a retirement fund. Retirement plans also often have the benefit of being tax-deferred. The longer you get to keep your money (and make interest on it) the better. It's never too early to start planning for retirement.
This is an example of passive income that isn't quite as passive as it may seem. Yes, if you own one or more homes or apartments you can collect regular rent checks from your tenants. But in exchange for that, you need to keep the properties in good working order, along with insuring and paying taxes on them. You may need to chase down rent checks from some tenants, too, and you may have several months without rent checks when you're between tenants.
As an Instacart personal grocery shopper, you will actually be doing the grocery shopping yourself (so don’t crush anyone’s avocados!). Your compensation depends on several factors, like the average size of your orders and average number of miles driven per trip. You can also get tips in addition to the pay that comes directly from Instacart (most people report an average earnings rate of $15 per hour).