I make the bulk of my money from blogging. In addition to the advertising revenue streams mentioned above, I also receive flat rate payments for blogging from various blogs throughout the web. I’m paid to write as a whistleblower, financial analyst, reviewer, commentator, and more. Writing for other sites builds traffic to my personal blog. The traffic for this blog gives me clout to present to advertisers.
But don't make the mistake of thinking this will be a passive source of income—you're on call whenever you have a guest and you'll always need to keep the place clean for incoming visitors. On top of just renting on Airbnb, consider offering your guests paid add-ons, like Lauren Gheysens', Royal Day Out in London, England—where she gives visitors a local's only tour of the city, complete with bespoke 18th century costumes.
The two popular ones are Poshmark and TheRealReal. Both make it dead simple to sell (and buy!) luxury items. The RealReal will pay you 60% of the sale price (more if you sell a lot) and Poshmark has a tiered commission structure. Sale prices under $15 pay a $2.95 flat fee and everything else is just 20%. Tradesy is another company and they take just 9%.
Try flipping houses if you have experience with making home repairs. As you may know from watching popular home improvement shows, flipping homes involves buying up a lower valued property that needs work, and then fixing it up for resell. To get started, you’ll need to have financing either through a bank a partner. Then, you can buy a property that’s priced below market value. After you renovate the property, you may be able to sell it for a profit.